CLASS X Important Questions Bank Magnetic effects of electric current

One mark Questions:
Part 1
1. How can you show that the magnetic field produced by a given electric current in the wire decreases as the distance from the wire decreases? 

2. What is the advantage of the third wire of earth connection in domestic appliances? 

3. What constitutes the field of a magnet?
4. What is short-circuiting in an electric supply?
5. What will be the frequency of an alternating current if its direction changes after every 0.01s?
 6. An alternating electric current has a frequency of 50 Hz. How many times does it change its direction in 1s?
7. How is the strength of the magnetic field at a point near a wire related to the strength of the electric current flowing in the wire?
8. How can it be shown that a magnetic field exists around a wire through which a direct current is passing?
9. On what effect of an electric current does an electromagnet work? 

10. What is the direction of magnetic field at the centre of a circular coil carrying current in anticlockwise direction?
Part -2
(Q.1) Passage of current through a straight conductor display some fixed pattern. Pick out the odd one ( 1 mark )
(a) Magnitude of the magnetic field produced at a given point increases as the current through wire increases
(b) The magnetic field produced by a given current in the conductor increases as the distance from it decreases
(c) Direction of the field lines is in accordance with the right hand thumb rule
(d) Field lines are unaffected by the quantity of current flowing.
(Q.2) The phenomenon of electro-magnetic induction is ( 1 mark )
(a) The process of generating magnetic field due to a current passing through a coil.

(b) Producing induced current in a coil due to relative motion between the magnet and the coil.
(c) The process of rotating a coil.  

(d) The process of charging a body. 

(Q.3) A magnetic field cannot exert any force on a( 1 mark )
(a) Moving magnet     (b) Stationary magnet      (c) Stationary charge(d) Moving charge
 (Q.4) Degree of closeness of the magnetic field lines signifies:( 1 mark )
 (a) Number of magnetic fields                                   (b) Distance between different magnetic fields
 (c) Relative strength of the magnetic field                (d) Direction of the magnetic field
(Q.5) What is a magnet? ( 1 mark )
(Q.6) What is the SI unit of induced current? ( 1 mark )
(Q.7) What is the frequency of d.c current? ( 1 mark )
(Q.8) What is the frequency of a.c current that you use in your house? ( 1 mark )
(Q.9) What is magnetic field? ( 1 mark )
(Q.10) There is a battery operated toy, what kind of motor is being used in it? ( 1 mark )
(Q.11) Give two example of devices in which d.c motor is used. ( 1 mark )
(Q.12) Give two examples in which a.c motor is used. ( 1 mark )
(Q.13) What is generator? ( 1 mark )
(Q.14) What is motor? ( 1 mark )
(Q.15) When the current in a wire moves from south to north, the direction of the deflection in the magnetic needle parallel to the wire will be:( 1 mark )
(a) East to west            (b) West to east         (c) East to north              (d) West to south
(Q.16) Magnetic field is a quantity that has both direction and magnitude. Pick out the incorrect statement( 1 mark )
(a) The magnetic field lines emerge from north pole and merge at the south pole.
(b) Inside the magnet, the direction of field lines is from its south pole to its north pole.
(c) Inside the magnet, the direction of field lines is from its north pole to its south pole.
(d) No two field lines intersect each other and the field is strongest where the field lines are crowded.
(Q.17) The region surrounding a magnet, in which the force of the magnet can be detected is said to have( 1 mark )
(a) Magnetic field          (b) Electric field            (c) Magnetic poles           (d) Electric poles
(Q.18) Which of the following is not the special features of magnets? ( 1 mark )
(a) They align in the North –South direction when suspended freely.
(b) They have two distinct North and South poles.

(c) Like poles attract each other and unlike poles repel each other.
(d) The magnetic field lines produced due to a magnet are closed curves.
(Q.19) Direction of the force experienced by a current-carrying conductor when placed in a magnetic field is dependent on ( 1 mark )
(a) Direction of the current alone            

(b) Direction of the magnetic field alone
(c) Direction of current as well as the direction of magnetic field
(d) Direction of electric field
(Q.20) The magnitude of the force experienced by a current-carrying conductor when placed in a magnetic field will be( 1 mark )
(a) Maximum if the directions of current and magnetic field are perpendicular to each other
 (b) Minimum if the directions of current and magnetic field are perpendicular to each other
 (c) Maximum if the directions of current and magnetic field are opposite to each other (d) Maximum if the directions of current and magnetic field are same
(Q.21) Which of the following is not true for an electric generator( 1 mark )
(a) Converts mechanical energy into electrical energy.
(b) Works on the basis of electromagnetic induction.
(c) Can be used to generate AC or DC.
(d) Converts electrical energy to mechanical energy
(Q.22) An alpha particle is projected towards west and gets deflected towards north by a magnetic field. The direction of the magnetic field is ( 1 mark ) 

(a) Towards south                   (b) Towards east             (c) Downwards            (d) Upwards
(Q.23) An electric current through a metallic conductor produces a/an _________ around it. ( 1 mark )
(a) Electric field          (b) Magnetic field            (c) Electromagnetic effect. (d) Gravitational field
(Q.24) A straight conducting wire is placed parallel to and over a compass needle. The deflection in the needle ( 1 mark )
(a) Becomes opposite when the direction of the current is reversed

(b) Remains in the same direction even on reversing the direction of current

(c) Keeps fluctuating on passage of current in any direction
(d) Is negligible on reversing the direction of current
(Q.25) At every point of a current carrying circular loop, the concentric circles representing the magnetic fields around it would become( 1 mark )
(a) Larger and larger as we move away from the wire.
(b) So large at the centre of circular loop that they look like straight lines.
(c) Smaller and smaller as we go away from the wire.
(d) There is no fixed pattern for circles
(Q.26) Which of the following statements is not true?( 1 mark )
(a) The pattern of the magnetic field around a conductor due to an electric current flowing through it depends on the shape of the conductor.

(b) The magnetic field of a solenoid carrying a current is similar to that of a bar magnet.
(c) Magnitude of magnetic field is directly proportional to the quantity of current flowing through the current.
(d) Magnetic field produced by the passage of current through a straight wire is permanent.
(Q.27) Magnetic field produced inside a solenoid are so strong that ( 1 mark )
(a) They can be used to magnetize a magnetic material, when placed inside the coil.
(b) They can be used to magnetize a magnetic material, when placed near the coil.
(c) They are still not able to magnetize a magnetic material. (d) They become permanent.
(Q.28) Increase in number of turns of a coil in the solenoid will( 1 mark )
(a) Have no effect on the strength of magnetic field   (b) Will add to the strength of the magnetic field
 (c) Will decrease the strength of the magnetic field    (d) Will change the direction of the magnetic field
(Q.29) An electromagnet consists of a core of ___________ wrapped around with a coil of ________ copper wire.( 1 mark )
(a) Soft iron, insulated     (b) Aluminum, Insulated     (c) Soft iron, uncovered (d) Magnet, uncovered
(Q.30) A current-carrying conductor when placed in a magnetic field experiences ( 1 mark ) 

(a) An acceleration   (b) A force          (c) Demagnetization    (d) It always remains in equilibrium
(Q.31) An electric motor is a device( 1 mark )
(a) That converts electrical energy into kinetic energy
(b) That converts electrical energy to mechanical energy
(c) There is no energy conversion of one form to another.
(d) That converts sound energy to light energy.
(Q.32) Which of the following statements cannot be related to the construction of an electric motor? ( 1 mark )
(a) A rectangular coil of insulated copper wire is placed between the two poles of a magnetic field such that two of its parallel sides are perpendicular to the direction of the magnetic field.
(b) The ends of the coil are connected to the two halves of a split ring.
(c) The inner insulated sides are attached to axle whereas the external conducting edges touch two conducting stationary brushes.

(d) The coil and the axle continuously rotate in one direction.
(Q.33) The direction of the induced current is given by( 1 mark )
(a) Right Hand Thumb Rule
 (b) Fleming’s Left Hand Rule
(c) Fleming’s Right hand Rule
(d) Faraday's law
(Q.34) According to Fleming’s Right Hand Rule, if we stretch the thumb, forefinger and middle finger of right hand – forefinger indicates direction of magnetic field, thumb shows the direction of motion of conductor, and then the middle finger will show the direction of ( 1 mark )
(a) Induced current        (b) Magnetic Force    (c) Alternating Current   (d) Electric force
(Q.35) The induced current is highest when ( 1 mark )
(a) Direction of motion of coil is at 900 to the magnetic field.
(b) Direction of motion of coil is at 300 to the magnetic field.
(c) Direction of motion of coil is at 600 to the magnetic field.
(d) Direction of motion of coil is at 1800 to the magnetic field.
(Q.36) Parameters of electricity supply in India are ( 1 mark )
(a) Potential Difference of 220 V, Frequency of 50 hertz and Current Rating of 5A/15A
(b) Potential Difference of 150 V, Frequency of 40 hertz and Current Rating of 10 A
(c) Potential Difference of 220 V, Frequency of 60 hertz and Current Rating of 15A
(d) Potential Difference of 220 V, Frequency of 40 hertz and Current Rating of 5 A
(Q.37) Pick the incorrect statement regarding fuse. Fuse is used for protecting the circuits due to ( 1 mark )
(a) Short-circuiting   (b) Overloading of circuits   (c) Faulty connections  (d) Theft
(Q.38) Which of the following will not cause overloading? ( 1 mark )
(a) Accidental hike in the supply voltage  b) Connecting many appliances to a single socket
 (c) Melting of fuse     (d) Short circuiting
Two marks Questions: 1. With the help of a neat-diagram, describe how you can generate induced current in a circuit.
2. What is meant by the term “Magnetic field Lines”? List two properties of magnetic field lines.
3. Write the rule which determines the direction of magnetic field developed around a straight
conductor when current is passed through the conductor.
4. State the rule to determine the direction of magnetic field produced around a current carrying
conductor.
5. On which factors does the force experienced by a current carrying conductor placed in a uniform
magnetic field depend?
6. State Fleming’s right-hand Rule.
7. Why is series arrangement not used for domestic circuits?
8. Differentiate between electric force and magnetic forces.
9. How does AC differ from DC? What are the advantages and disadvantages of AC over DC?
10. Draw the magnetic field due to a current carrying circular coil. State the clock rule to find the
polarities of the faces of the coil.
11. What will be the frequency of an alternating current, if its direction changes after every 0.05 sec?
12.What is the principle on which working of electric generator is based? What are its important part?.
13.Why two magnetic lines of forces don’t intersect each other?
14. Give two methods with which we can increase the strength of magnetic field produced by a circular coil carrying current?
Three Mark Questions 

1. Draw the pattern of field lined due to a solenoid carrying electric current. Mark the north and the south poles in the diagram.
2. Draw the pattern of lines of force due to a magnetic field through and around a current carrying loop of wire. How would the strength of the magnetic field produced at the centre of the circular loop be affected if 

(i) the strength of the current passing through this loop is doubled? 

(ii) the radius of the loop  is reduced to half of the original radius?
3. Draw the pattern lines of force due to a magnetic field associated with a current carrying conductor. State how the magnetic field produced changes 

(i) with an increase in current in the conductor and

(ii) the distance from the conductor.
4. Draw the pattern of field lines due to a bar magnet. Mention any two properties of the magnetic field  lines. 

5. How does the strength of the magnetic field at the centre of a circular coil of wire depend on:

 (i) the radius of the coil? 

(ii) the number of turns of the wire? 

(iii) the strength of the current flowing in the coil?
6. The flow of a current in a circular loop of a wire creates a magnetic field at its centre. How can
existence of the field be detected? State the rule which helps to predict the direction of this magnetic
field.
7. What are the factors on which the strength of magnetic field produced by current-carrying solenoid
depends?
8. A coil of copper wire is connected to a galvanometer. What would happen if a bar magnet is: 

(i) pushed into the coil with north pole entering first 

(ii) pulled out of the coil 

(iii) held stationary inside the coil?
9. Explain what is short-circuiting and overloading in an electric supply.
10. What are magnetic field lines? How is the direction of a magnetic field at a point determined?
11.What are the factors which govern the force experienced by a current carrying conductor placed in a uniform magnetic field depends? ( 3 Marks )
12. Distinguish between an electric motor and generator?
13.What is direct current (d.c) and alternating current (a.c).
14.A current of 2 A flows through a circular coil of radius of 4 cm, and has 10 turns. The coil is
aligned horizontally and current flows though the coil in clockwise direction. Find the magnitude and
direction of magnetic field at the centre of the coil due to the current.
Five Mark Questions:
1. (a) Suggest an activity to show the pattern of magnetic field lines, when you are provided with a bar magnet, a cardboard piece and iron filings

(b)Draw a rough sketch of the field lines which you will observe.
2. (a) What is an electromagnet? What does it consists of? 

(b) Name one material in each case used to make a

 (i) permanent magnet (ii) temporary magnet. 

(c) Describe an activity to show how can you make an electromagnet in your school lab?
3. State Fleming’s left-hand rule. With a labeled diagram, describe the working of an electric motor. What is the function of split-ring Commutator in a motor?
4. State Fleming’s right-hand rule. With a labeled diagram, describe the working of an AC electric generator.
5. Draw the lines of force of the magnetic field through and around (a)single loop of wire carrying current, (b) a solenoid carrying electric current.
6. Why is pure iron not used for making permanent magnets? Name one material used for making permanent magnets. Describe how permanent magnets are made electrically. State two examples of electrical appliances made by using permanent magnets.
7. (a)Draw a schematic labeled diagram of a domestic wiring circuit which includes (i)a main fuse (ii) a power meter (iii)one light point (iv) a power plug.(b) Why is it necessary to connect an earth wire to electric appliances having metallic covers?
8. (a)What are magnetic field lines? How is the direction of a magnetic field at a point determined? (b) Draw two field lines around a bar magnet along its length on its two sides and mark the field directions on them by arrow marks. (c) List any three properties of magnetic field lines.
9. What is an electric motor? With the help of a diagram, describe the working of an electric motor.
10. What are magnetic field lines? Write their characteristics. Draw the magnetic field lines due to a current flowing in a circular coil.
11. Explain the principle, construction and working of an electric motor.
12. Explain with labeled diagram, the principle, construction and working of an electric generator.
13. (a ). What is an electromagnet ?    (b). List any of its two uses.
(c ). Draw a labeled diagram to show how an electromagnet is made.
(d ). What is the purpose of the soft iron core used in making an electromagnet ?
14.A solenoid is 1 m long and 2 cm in diameter has 50 turns/cm. A current of 5 A is flowing through it. Calculate the magnetic induction:    a) Inside the solenoid.   b) At one end on the axis of solenoid.
15. Explain the construction and working of electric motor?
16. What is the principle behind the working of electric generator? Explain its working with the help of well labeled diagram.
17. The mains power supply of a house is through a 5-A fuse. How many 100-W bulbs can be used in this house at the correct voltage?
18. A wire 10 cm long and carrying a current of 1.5 A is held in a uniform magnetic field in which B=10-3 T. Calculate the force on the wire if it is held perpendicular to the lines of the magnetic field.
19 A current of 10 A flows in a circular coil of 1000 turns and radius 0.1 m. Find the magnitude of the magnetic field at the centre of the coil.
20. At what distance from a straight conductor carrying a current of 2.8 A, will the magnetic induction be 2.8×10-5 T?
21. Find the strength of the current which will produce a magnetic field of 10-4 T at the centre of a coil of mean radius 0.10 m. The coil comprises 20 turns.
22. A 0.4 m wire, stretched horizontally, carries an electric current of 15 A from East to West, in a magnetic field whose magnetic field intensity is 0.1 N/Am, directed vertically downwards. What is (a) the magnitude of the magnetic deflecting force on the wire, and (b) its direction?

WHAT IS PHYSICS?

Physics is the scientific study of matter and energy and how they interact with each other.
This energy can take the form of motion, light, electricity, radiation, gravity . . . just about anything, honestly. Physics deals with matter on scales ranging from sub-atomic particles (i.e. the particles that make up the atom and the particles that make up those particles) to stars and even entire galaxies.

How Physics Works

As an experimental science, physics utilizes the scientific method to formulate and test hypotheses that are based on observation of the natural world. The goal of physics is to use the results of these experiments to formulate scientific laws, usually expressed in the language of mathematics, which can then be used to predict other phenomena.

The Role of Physics in Science

In a broader sense, physics can be seen as the most fundamental of the natural sciences. Chemistry, for example, can be viewed as a complex application of physics, as it focuses on the interaction of energy and matter in chemical systems. We also know that biology is, at its heart, an application of chemical properties in living things, which means that it is also, ultimately, ruled by the physical laws.

QUESTION BANK Class 9th Physics (Forces and Laws of motion)

CBSE PHYSICS Class IX ASSIGNMENT Forces and Laws of motion)                        

1. What do you mean by a force?
2. Give an example of a balanced force?
3. Can force change the shape of an object? Give an example to prove your point?
4. Do action and reaction force react in the same direction?
5. Why a moving ship does takes longer time as compared to a car when equal breaks are applied?
6. Why are passengers through in forward direction when a running bus stops suddenly?
7. Why do passengers tend to fall sideways when the bus takes a sharp u turn?
8. Why should a passenger hold on to prevent himself from swaying in a turning bus?
9. Why do passengers tend to fall back when it starts suddenly?
10. Why do passengers jumping out of a rapidly moving bus fall forward with his face downwards, if he does not run forward?
11.  Why does a passenger jumping out of a rapidly moving bus fall forward with his face downwards?
12. Why can dust be removed by shaking it, or beating it by a carpet?
13.  Why does a bullet when fired against a glass window pane make a hole in it, and the glass pane will smash it?

QUESTION BANK Class X Physics (Electricity)

CBSE PHYSICS  QUESTION BANK Class X Physics (Electricity)

Very short answer questions (1 mark) 

1. Give the unit of (a) Charge (b) Current

2. Define current

3. Name the unit of (a) electrical resistance (b) resistivity

4. Define One Ohm

5. Define Resistivity

6. What is the resistance of a torch bulb rated at 2.5 V and 500 mA?

7. Two resistances of each 2 ohm are connected in parallel. Find their equalent resistance.

8. On what factors does the resistivity of a material depend?

9. Plot a graph between the Potential difference V and current I through a conductor 

10. What happens to the resistance of the circuit if the current through it is doubled?

Short answer questions (2 marks)

1. Two wires of same material are having length L and 2L. Compare their resistance and resistivity.

2. Why are coils of electric toaster and electric iron made of an alloy rather then a pure metal?

3. Two wires are of same length and radius but one of them is copper and the other is of iron. Which will have more resistance? (Given the resistivity of copper = 1.62 x 10 -8 ohm meter and resistivity of iron = 10 x 10-8 ohm meter.

4. Define 1KWh. Give the relation between 1kwh and Joule.

5. State which has a higher resistance. A 50W or 25W lamp. Also find the ratio of their resistances.

6. A wire of resistance 5 Ohm is spent in the form of closed circle. What is the resistance between 2 points at the ends of any diameter of the circle?

7. Calculate the amount of charge that would flow in one hour through the element of an electric irondrawing a current of 0.4 amps.

8. A electric toaster of resistance 20 Ohm takes a current of 5A. Calculate the heat developed in 30 s.

9. A bulb is rated at 5V, 100mA. Calculate its (1) Power (2) Resistance

10. Name two special characteristics of a heater coil.

Short answer questions (3 marks)

1. Define resistance and resistivity. Give the relation between them. Explain the dependence of resistance on temperature.

2. With the help of neat circuit, derive the expression for the equalent resistance of 3 resistances connected in series.

3. With the help of neat circuit, derive the expression for the equivalent resistance of 3 resistances connected in parallel

4. (a ) Draw the circuit consisting of a battery of five 2V cells, 5ohm resistor, 10 ohm resistor, 15 ohm resistor and a plug key. All connected in series (b) Calculate the current passing through the above circuit when key is closed.

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QUESTION BANK Class X Physics (Electricity)

QUESTION BANK Class X Physics (Electricity)

CBSE PHYSICS

Electricity Practice Questions for CBSE

1. Define electric potential difference?

2. Why is an ammeter connected in series in a circuit?

3. Why is a voltmeter connected in parallel in a circuit?

4. State the law that governs the strength of the current passing through a metallic conductor when a p.d is applied across its end. Illustrate this law graphically?

5. State the law which governs the amount of heat produced in a metallic conductor when current is passed through it for a given time. Express this law mathematically?

6. Define resistance. What are the factors on which it depends?

7. A copper wire of resitivity P is stretched to reduce its diameter to half its previous value. What is the new resistivity?

8. Define the S I unit of electric current and potential difference.

9. Derive expressions for equivalent resistance of resistors connected in

a. series combination

b. parallel combination

common science questions

CBSE PHYSICS
What influence does the moon have on the Earth?
The main effect of the moon on Earth is its influence on tides. Ocean tides result because the side of the Earth that is facing the moon is affected by the moon's gravity more than the center or opposite side. This creates the effect of ocean water constantly being attracted to two bulges on opposite sides of the Earth, thus creating the tides.
How hot is the sun?
The surface of the sun is 5,778 K, or 9,941 degrees Fahrenheit. The core of the sun, however, is a staggering 15,700,000 K, or 28,259,540 degrees Fahrenheit. The Earth is just far enough away from the sun to not burn up and just close enough to not turn into a frozen wasteland. Other planets in our solar system are uninhabitable because of their proximity to the sun.
What is an endangered species?
An endangered species is defined as any species at risk of extinction. This can be caused by dwindling numbers or impending environmental changes. Although the term endangered species is used in a broad manner, there are other classifications within the larger category of threatened organisms, including vulnerable and critically endangered. Examples of endangered species include blue whales, snow leopards, tigers, and the albatross.
How many types of insects are there?
Six and 10 million unique species of insects are in existence on our planet. However, only around 1 million of these have been officially discovered. Among discovered insects, beetles are greatest in number, with around 360,000 unique species. A total of 170,000 species of butterflies have been recorded, while only 300 types of webspinners have been discovered.
What is global warming?
Global warming is a description of the increase in Earth's surface temperature. This phenomenon has been noticed since the mid-1900s, and is predicted to continue unless humans do something to curb or reverse it. Global warming is widely acknowledged to be a result of the greenhouse effect: as our atmosphere grows thicker with greenhouse gases, such as carbon dioxide, the sun's rays penetrate the atmosphere, reflect off of the Earth's surface, and are then unable to pass back through the atmosphere, heating up the earth.

CBSE PHYSICS

General Science Questions and Answers

No.	Question	Answer
1	The theory of relativity was propounded by	Albert Einstein
2	The principal metal used in manufacturing steel is	Iron
3	An altimeter is used for measuring	Altitude
4	Oology is the study of	Bird Eggs
5	Radioactivity was discovered by	Henry Bacquerel
6	The metal used in storage batteries is	Lead
7	The instrument used to measure the relative humidity of air is	Hygrometer
8	Barometer was invented by	Torricelli
9	The unit of power is	Watt
10	Radium was discovered by	Marie and Pierrie Curie
11	The existence of isotopes was discovered by	Frederick Soddy
12	Dynamo was invented by	Michael Faraday
13	The nuclear reactor was invented by	Enrico Ferni
14	The law of gravitation was propounded by	Sir Isaac Newton
15	Crescograph was invented by	J.C.Bose
16	Crescograph is used to measure the	Rate of growth of a plant
17	Galileo's first scientific discovery was	Pendulum
18	Microscope was invented by	Aaton Van Leewen Hock
19	The scientist who is known as father of modern biology is	Aristotle
20	The first person to see a cell under microscope was	Robert Hooke
21	The smallest flowering plant is	Worffia
22	The four blood groups were discovered by	Karl Landsteiner
23	Sodium was discovered by	Sir Humphry Davy
24	The atomic number of oxygen is	Eight
25	The basic building blocks of proteins are	Amino acids
26	The botanical name of the cotton plant is	Gossipium Hirsutum
27	An Electroscope is used to	Detect charges on a body
28	The unit of loudness is	Phon
29	An ammeter is used to measure	Electric current
30	Plant that eat insects are called	Insectivorous plants
31	Fruits that are formed without fertilization are called	Parthenocarpic
32	Plants that flower only once in their lifetime are called	Mono carpic
33	The botanical name for rice is	Oryza Sativa
34	Penicillin is obtained from	Mould
35	The largest tree in the world is	Seguoia Gigantica
36	Herpetology is the study of	Reptiles
37	Entomology is the study of	Insects
38	Ornithology is the study of	Birds
39	Ichtyology is the study of	Fishes
40	Osteology is the study of	Bones
41	The botanical name for brinjal is	Solanum melongenal
42	The botanical name for onion is	Allium Cepa
43	The study of sound is called	Acoustics
44	The study of heavenly bodies is called	Astronomy
45	The study of tissues is called	Histology
46	Electric Lamp was invented by	Thomas alva Edison
47	The fear of crowd is called	Ochlophobia
48	The fear of books is called	Bibliophobia
49	The fear of going to bed is called	Clinophobia
50	The symbol of gold is	Au
51	The symbol of sodium is	Na
52	The symbol of Sr stands for	Strontium
53	The symbol Rb stands for	Rubidium
54	The symbol Md stands for	Mendelevium
55	Calcium sulphate is commonly called	Plaster of Paris
56	Sodium carbonate is commonly called	Washing Soda
57	Sodium chloride is commonly known as	Common Salt
58	The chemical name of Chloroform is	Trichloromethane
59	The chemical name of baking powder is	Sodium bicarbonate
60	The chemical name of bleaching powder is	Calcium hypochlorite
61	The formula HCL stands for	Hydrochloric Acid
62	The formula H2SO4 stands for	Sulphuric Acid
63	The formula CHCI3 stands for	Trichloromethane
64	The formula H2O2 stands for	Hydrogen peroxide
65	A fungus which can only survive on other living organisms is called	Obligate Parasite
66	A plant which lives in the dark is called	Scotophyte
67	A plant adapted to live in dry places is called a	Xerophyte
68	A plant adapted for growth in water is called a	Hydrophyte
69	Bifocal lens was invented by	Benjamin Franklin
70	Cement was invented by	Joseph Aspdin
71	Laser was invented by	Dr.Charles H.Townes
72	Electromagnet was invented by	William Sturgeon
73	Rayon was invented by	Sir Joseph Swann
74	Thermostat is an instrument used for regulating	Constant temperature
75	The science of organic forms and structures is known as	Morphology
76	Phycology is the study of	Algae
77	Tata Institute of Fundamental Research was established in	1945
78	CSIR stands for	Council of Scientific and Industrial Research
79	ISRO stands for	Indian Space Research Organisation
80	The first human being to land on moon was	Neil Armstrong
81	The first Indian in space was	Rakesh Sharma
82	ISAC stands for	ISRO Satellite Centre
83	VSSC stands for	Vikram Sarabhai space Centre
84	The headquarters of ISRO is located at	Bangalore
85	VSSC is located at	Thiruvananthapuram
86	ISAC is located at	Bangalore
87	National Science Centre is located at	New Delhi
88	Central Tobacco Research Institute is located at	Rajahmundry
89	Indian Institute of Horticultural Research is located at	Bangalore
90	The Atomic Energy Commission was set up in	August 1948
91	The first Indian Satellite was	Aryabhatta
92	The first Indian Satellite was launched in the year	1975
93	ASLV stands for	Augmented Satellite Launch Vehicle
94	INSAT stands for	Indian National Satellite
95	The fear of women is known as	Gynophobia
96	The fear of men is known as	Androphobia
97	The scientist who developed the Quantum theory was	Max Plonck
98	The steam engine was invented by	James Watt
99	The botanical name of tea is	Camellia Sinensis
100	Logarithms were devised by	John Napier
101	The acid used in a car battery is	Sulphuric acid
102	The system for writing by blind people was invented by	Louis Braille
103	The parachute was used for the first time by	J.P.Blanchard
104	The German physicit who first demonstrated the existence of Radio waves was	Henrich Hertz
105	The instrument that records the intensity of earthquakes is	Seismograph
106	The laws of floating bodies was discovered by	Archimedes
107	The density of milk is measured by a	Lactometer
108	Fountain pen was invented by	L.E.Waterman
109	The instrument used to measure the pressure of gases is the	Monometer
110	Bhaskara I was a famous	Astronomer
111	The first atomic power station established in India was the	Tarapore Atomic Power Station
112	The role of heredity was demonstrated by	Mendel
113	The instrument used to measure the concentration of salt water is the	Salinometer
114	Spectroscopy is the study of	Anders John Angstrom
115	Dactylography is the study of	Finger Prints
116	A tangent galvanometer is used to study the	Strength of direct current
117	The fruit of Oak is called	Acron
118	ZETA stands for	Zero Energy Thermonuclear Assembly
119	The formula C6H5OH stands for	Phenol
120	Michael Faraday worked as an assistant under another scientist whose name was	Sir Humphry Davy
121	Vulcanised rubber was invented by	Charles Goodyear
122	The symbol Zn stands for	Zinc
123	The symbol He stands for	Helium
124	Celluloid was invented by	A.Parker
125	Glider was invented by	Sir George Caley
126	Safety matches was invented by	J.E.Lundstrom
127	Radio valve was invented by	Sir J.A.Fleming
128	Space Applications Centre is located at	Ahmedabad
129	Atomic Energy Commission is located at	Mumbai
130	Dynamics is the study of	Movements of bodies
131	Statics is the study of	Forces acting on bodies at rest
132	Mechanics is the study of	Forces acting on bodies
133	Zoology is the study of	Animal life
134	Botany is the study of	Plant life
135	Psychology is the study of	Human mind
136	The first American to orbit earth was	John H.Glen
137	The electro-cardiograph was invented by	William Einthoven
138	The molecular formula of cane sugar is	C12H22O11
139	A compound which contains only hydrogen and Carbon is called a	Hydrocarbon
140	The liquid used to preserve specimens of plans and animals is	Formalin
141	The law of segregaton was propounded by	Mendel
142	Auriscope is used to detect	Ear disorders
143	The three states of matter are	Solid,liquid and gas
144	The scientific name for blood platelets is	Thrombocytes
145	The response of a plant to heat is called	Thermotropism
146	The response of a plant to touch is called	Trigmotropism
147	The symbol Zr stands for	Zirconium
148	Nickel was discovered by	Cronstledt
149	Manganese was discovered by	Gahn
150	The common name for pottasium carbonate is	Potash
151	Bismuth was discovered by	Valentine
152	The biggest plant seed is	Cocodemer
153	Toxicology is the study of	Poisons
154	Virology is the study of	Viruses
155	Paleontology is the study of	Fossils
156	Calorimeter is used to measure	Quantity of heat
157	Chronometer was invented by	John Harrison
158	Stethoscope was invented by	William Stockes
159	Spinning frame was invented by	Sir Richard Arkwright
160	Al stands for	Aluminium
161	Gd stands for	Gadolinium
162	Ir stands for	Iridium
163	Bi stands for	Bismuth
164	The Chemical formula of sodium bicarbonate is	NaHCO3
165	The chemical formula of common salt is	Nacl
166	The chemical formula of washing soda is	Na2CO3,IOH2O
167	The chemical formula of lime soda is	CaCO3
168	The chemical formula of chloroform is	CHcl3
169	The study of grasses is known as	Agrostology
170	The study of antiquities is known as	Archaeology
171	The study of the duration of life is known as	Chronobiology
172	The study of bacteria is known as	Bacteriology
173	Nylon was invented by	Dr.Wallace H.Carothers
174	Electric razor was invented by	Jacob Schick
175	The symbol of silver is	Ag
176	The symbol of silicon is	Si
177	The symbol of titanium is	Ti
178	Calcium oxide is commonly known as	Quick lime
179	A deviation of light passing from one medium to another is known as	Refraction
180	An apparatus for generation of atomic energy is called a	Reactor
181	A machine used for converting mechanical energy into electrical energy is called a	Generator
182	The first Indian woman in space was	Kalpana Chawla
183	The revolver was invented by	Samuel Colt
184	The refrigerator was invented by	J.Perkins

Everyday Science

CBSE PHYSICS

Everyday ScienceScientific, Geographical and Astronomical Phenomena
(Questions and Answers)

Q. Why does a piece of iron get rusted if left exposed in the open ?Ans. Iron piece rusts if left exposed in the open because it reacts with the oxygen in the air, forming iron oxide—a compound of Iron and oxygen.

Q. Why can petrol fire not be put out with water ?Ans. Petrol is a hydro carbon which remains isolated with water and is having less density. So when water is poured petrol floats on it and keeps on burning. The temperature of the burning petrol is so high that the water poured on the petrol fire is evaporated before it extinguishes the fire.

Q. Ice packed is saw dust does not melt quickly. Why ?
Ans. Saw dust is a bad conductor of heat and protects the ice from the external heat and hence from melting away quickly.

Q. White light passing through a glass prism gives rise to a coloured pattern on the wall. Why ?
Ans. White light is made up of seven colours. Rays of different colours refract or bend along different paths and fall on different points on the wall forming a coloured pattern known as spectrum.

Q. A boatman pushes the bank with his pole. Why ?Ans. Action and reaction being equal and opposite, the bank will push the boat away from it.

Q. A burning candle gets extinguished when covered with a tumbler. Why ?Ans. A burning candle gets extinguished when covered with a tumbler because the supply of oxygen is cut-off and the flame goes out.

Q. Why do you see rainbow after rain ?Ans. The water drops suspended in the atmosphere act as prism and disperse light into seven colours.

Q. A metal tea-pot has an ebony handle. Why ?
Ans. Ebony being bad conductor of heat, the handle does not get hot.

Q. Why is one’s breath visible in winter, but not in summer ?Ans. In winter the water vapour contained in the breath condenses into small droplets of water, which become visible. In summer it is not so.

Q. The weight of a man on the surface of the moon will be only about one-sixth of his weight on the earth. Why ?Ans. The gravity of the moon is one-sixth that of the earth, hence the weight of a person on the surface of the moon will be onesixth of his weight on the earth.

Q. Why is it easier to roll a barrel than to pull it along the road ?Ans. Slipping resistance is much more than rolling resistance.

Q. Why is the flash of lightning seen before the sound of thunder is heard ?Ans. Because light travels faster than sound.

Q. How does a soda water straw work ?
Ans. When we suck through a soda water straw, low pressure is created inside the straw. The liquid outside rushes into balance the difference.

Q. Small space is left between each set of two rails of a railway line.
Ans. Iron expands when it gets hot. A small space is left between the ends of the rails in order to allow the expansion of rails due to heat.

Q. How does bulb emit light ?
Ans. The current passes through a wire of high resistance which becomes red hot, and emits light.

Q. What is an electric fuse ? What purpose does it serve ?
Ans. A thin wire used in maintaining the condition of the energy; it prevents overloading of energy.

Q. How does a thermos flask keep a hot liquid hot and cold liquid cold ?Ans. It is a double-walled vessel in which the inner surface of the outer vessel and the outer surface of the inner vessel are silvered so as to prevent radiation of heat. The space between the walls of the two vessels is made of vacuum to prevent the escape of heat by conduction or convection.

Q. A parachute enables a person to descend in safety in case of an accident to aircraft ?Ans. A man falls to the earth because of the gravitational pull of the earth. The parachute offers considerable resistance to that gravity, thereby slowing down the speed of the descending man. The parachute thus enables a person to descend in safety.

Q. A person in a moving vehicle is thrown forward when the vehicle stops suddenly. Why ?
Ans. When a moving vehicle stops suddenly, a passenger will tend to fall forward because the lower part of his body in contact with the seat comes to stop suddenly but the upper part of his body is still in motion sharing the movement of the train. So on account of inertia, the passenger falls forward.

Q. A plane approaching at a speed of 1000 m.p.h. is not heard. Why ?Ans. Sound travels at a speed of 760 m.p.h., hence a plane approaching at a speed of 1000 m.p.h. cannot be heard.

Q. Why does an electric bulb make a bang when it is broken ?Ans. An electric bulb has a partial vacuum. When it is broken, air rushes into take the place of the vacuum, hence it bangs.

Q. Why does a ship made of steel float though a steel ball sinks ?Ans. The ship displaces more water then its own weight whereas the weight of the water displaced by a steel ball is much less than the weight of the steel ball.

Q. Why do the stars twinkle ?Ans. The stars seem to twinkle due to two causes. First the light from the stars passes through several mediums; secondly our vision has a tendency to distract.

Q. Why is it easier to swim in a sea than in a river ?
Ans. The density of the sea water is higher than the density of the river water.

Q. Why is hot soup more tasty than the colder one ?
Ans. As temperature is increased, surface tension decreases and the liquid now occupies more area. Thus the hot soup occupies more area on the tongue and is, therefore, more tasty than the colder one.

Q. Thick glass tumblers often crack when very hot liquids are poured into them. Why ?Ans. The inner layer tends to expand more rapidly than the outer layer thus producing phenomenon of unequal expansion resulting in cracks due to the resulting pressure.

Q. Why does water get cooled in an earthen pitcher ?Ans. Pitchers have pores through which water percolates which evaporates. During evaporation heat is taken away and the water gets cooled.

Q. Why does the sky and the water of the ocean look blue ?
Ans. The blue part of the sunlight is scattered by the particles of the atmosphere around, while other parts of light pass through it : that is why the sky looks blue because of the refraction of the blue light only.

Q. Which will reach the ground first : a bullet which is shot horizontally from a gun or similar bullet thrown upward from the ground ?
Ans. Obviously horizontally shot bullet is to come down first. Its direction is perpendicular to that of gravitational force. So both vector will not affect each other but in the case of a bullet shot upward has velocity vector in the opposite direction of gravitation force. So it will take more time.

Q. Why does an iron gain weight on rusting ?Ans. The rusted iron is nothing but iron-oxide. Iron in the presence of moisture absorbs oxygen from the atmosphere and forms iron oxide. The weight gained is equal to the weight of oxygen absorbed.

Q. Why does hard water not readily form lather with soap ?
Ans. Hard water contains the sulphates and chlorides of magnesium and calcium, which form insoluble compounds with soap. Hence soap does not lather with hard water.

Q. Why are mountains cooler than plains ?Ans. It is so because, firstly, the air on the mountains is rare than that on the plains and absorbs less heat than the air on the plains, secondly the heat absorbed during the day on the mountains radiates away more quickly due to the rarity of the air, thirdly, major portion of the mountains remains in shade.

Q. Why is sea-water saline ?
Ans. The rivers in the course of their flow and falling into the sea bring with them deposits of salt and this process has been going on for lakhs of years, it makes sea-water saline.

Q. Glass when heated cracks while metal does not.
Ans. Glass being bad conductor of heat only that part is heated which comes into contact with heat while the other parts remain unaffected. This results in unequal expansion and hence the tension which cracks the glass. On the other hand, metal is a good conductor of heat and so all its bulk gets uniformly heated and hence no surface tension.

Q. Why does it not hurt when we cut our nails ?
Ans. Nails are the parts of the body which are not connected either with the blood vessels or cartilage and hence having no relation with the nervous system. Therefore cutting them does not give pain.

Q. A hydrogen balloon rises. Why ?
Ans. Hydrogen is lighter than air, the weight of the hydrogen balloon is less than the weight of the air displaced by it.

Q. Why is a compass used as an indicator of direction ?
Ans. The magnetic needle of the compass due to the influence of the earth’s magnetic field always lies in the north south direction. Hence we can known the direction.

Q. Why is a country like Ladakh, it may be very hot in sunshine, but bitterly cold in shade ?
Ans. The atmosphere on great heights like Ladakh is rarefied, which offers little obstacle to the rays of the sun which are therefore, scorching. But the rarefied air absorbs little heat from the rays of the sun, therefore, the atmosphere remains cold. Hence it is very cold in the shade.

Q. Why does a straight stick look bent when a part of it is immersed in water ?Ans. The rays of the light passing from a rare medium to a dense medium change their course due to refraction, where the rays coming from stick in water come in air at surface they get displaced away from perpendicular as our eyes see straight way so the stick seems bent.

Q. Why does water boil at a lower temperature on the hills than on the plains ?Ans. The higher the pressure, the higher boiling point : the lower the pressure the lower the boiling point. The atmospheric pressure on the hills is lower than that on the earth.

Q. Why does a rider feel a tendency to fall when the horse starts running of stops suddenly ?
Ans. This is caused by inertia. When the horse starts running, the rider, being at rest, falls back. When a running horse stops suddenly, the rider being in motion has a tendency to fall ahead.

Q. Why does a person carrying a bucket full of water in his right hand bend towards the left ?
Ans. He bends towards his left so that the centre of gravity falls within the base. This enables him to keep up balance, otherwise he may fall.

Q. Why does tea cool more rapidly in a saucer than in a cup ?
Ans. In a saucer evaporation takes place more rapidly than in a cup. Cooling is caused by evaporation.

Q. Ice packed in sawdust does not melt quickly. Why ?
Ans. Ice packed in sawdust does not melt quickly, because sawdust being bad conductor, it cuts the heat rays.

Q. Why do you heat a metal rim before fitting it to a wheel ?Ans. By heating, the rim expands and fits easily over a slightly bigger radius than that of the rim. On being cooled it contracts and has a firm grip on the wheel.

Q. Why do wet clothes dry slowly on a rainy day ?
Ans. On a rainy day the atmosphere air contains more water vapour than on a dry day and hence evaporation is slower.

Q. Why does a substance thrown up come to the ground ?Ans. Because of the gravitational force of the earth.

Q. Why does moisture gather outside of a glass of cold water on a warm day ?
Ans. The temperature of the outer surface of glass of cold water is lower than that of its surroundings. The vapour in the surrounding atmosphere gets condensed on the outer surface of the water and appears in the form of tiny particles of water.

Q. Why are we advised to empty the ink from our fountain pen before going up on aeroplanes ?Ans. A we go up higher and higher the air becomes rare and atmospheric pressure lower, so that the volume of the air inside the fountain pen will also increase and the ink will be pushed out thus spoiling the clothes and hence the advice.

Q. What happens to iron when it rusts ?Ans. It reacts with the oxygen of the air and forms iron-oxide which is the rust.

Q. How would you distinguish between welding and soldering ?Ans. Welding is the joining of metals by raising the temperature of the metals to fuse them together by metling their ends. Soldering is the joining of metals with the help of an alloy called solder.

Q. How does a ball which falls down, bounce up ?Ans. It is due to the operation of Newton’s Third Law of motion. To every action there is equal and opposite reaction. A ball falling to the ground is slightly deformed. Due to the elastic force of the material of which the ball is made, the ball tries to recover its original shape. In doing so it forces the ground which pushes the ball upward due to reaction and the ball bounces up.

Q. An iron nail floats on mercury but sinks in water. Give reasons.
Ans. The specific density of iron is lower than that of mercury, hence it floats on mercury, while it is higher than that of water, hence it sinks in water.

Q. How do you convert Centigrade in to Fahrenheit ?Ans. With the help of the following formula—
C/100 = F – 32/180

Q. It is advisable to work electric appliances when they are earthed suitably. Why ?Ans. In case of short-circuiting, the current passess to the earth without harming the user, if an electrical appliance is properly earthed.

Q. How does a refrigerator keep food fresh ?Ans. Food is kept fresh so long as fermentation does not set in; refrigerator prevents fermentation by providing low temperature.

Q. Ice wrapped in a blanket does not melt away quickly.
Ans. Blanket being bad conductor of heat prevents the outside heat from creeping inside.

Q. Why can a petrol fire not be extinguished by throwing water on it?Ans. The heat of the petrol fire is so intense that the water thrown on it gets evaporated and decomposed. Hence it is not effective in extinguishing the petrol fire.

Q. A train stops when the chain is pulled. Why ?Ans. When the chain is pulled, one small valve gets opened and air/atmospheric pressure is admitted to the under side of the piston head of the brake cylinder through pipe connections. Initially there is vacuum on both top and bottom side of the piston head. When the air/atmospheric pressure enters the under side of the piston head, the piston raises up due to difference of pressure and pulls the brake rigging to which it is connected with links and levers. Thus the brakes are applied and the train stops