Featured Posts

13 April 2014

CBSE Physics Numerical based on chapter - Electricity & its effects For (Class X)


NUMERICAL - Electricity and its effects For (Class X)

1. A resistance of 6 ohms is connected in series with another resistance of 4 ohms. A potential difference of 20 volts is applied across the combination. Calculate the current through the circuit and potential difference across the 6 ohm  resistance.
2. Calculate the number of electrons constituting one coulomb of charge per second through any cross section of a conductor.
3. How much work is done in moving a charge of 2 C across two points having a potential difference of 12 V ?
4. How much energy is given to each coulomb of charge passing through a 6 V battery ?
5. Calculate the work done in moving a charge of 5 Coulombs from a point at a potential of 210 Volts to another point at 240 Volts.
7. When a particle of charge 10 µC is brought from infinity to a point P, 2.0 mJ work is done by the external forces. What is the potential at P ?
9. How many electrons pass through a lamp in one minute if the current be 200 mA?
10. Calculate the current supplied by a cell if the amount of charge passing through the cell in 4 seconds is 12 C ?
11. A 2 Volt cell is connected to a 1 Ω resistor. How many electrons come out of the negative terminal of the cell in 2 minutes?
12. a)  How much current will an electric bulb draw from a 220 V source, if the resistance of the bulb filament is 1200 Ω ?
b)  How much current will an electric heater coil draw from a 220 V source, if the resistance of the heater coil is 100 Ω ?
13. The potential difference between the terminals of an electric heater is 60 Volts when it draws a current of 4 Ampere from a source. What current will the heater draw if the potential difference is increased to 120 Volt.  
14. A torch bulb when cold has 1Ω resistance. It draws a current of 0.3 Ampere when glowing from a source of 3 V. Calculate the resistance of the bulb when glowing and explain the reason for the difference in resistance.   

X Magnetic effects of currents [Conceptual Question with solution)

Question:
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
Solution:
Here , An electron beam, moving horizontally from back wall towards the front wall so, the direction of current will be in the opposite direction i.e. horizontally from front wall towards the back wall or towards us. The direction of the deflection of [EMF] is towards our right.
Let us use left hand Flemings rule: Adjust center finger point towards us (I) and thumb towards right side (EMF) then our forefinger will point in downward direction (MF)
Question:
A current through a horizontal power line flows in east to west direction. What is the direction of magnetic field at a point directly below it and at a point directly above it?
Solution
The current is in the east-west direction. Applying the right-hand thumb rule, we get that the direction of magnetic field at a point below the wire is from north to south. The direction of magnetic field at a point directly above the wire is from south to north
Question:
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Solution
In the following diagram the current is flowing clockwise. If we are applying right hand thumb rule to the left side of the loop then the direction of magnetic field lines inside the loop are going into the table while outside the loop they are coming out of the table. If we are applying right hand thumb rule to the right side of the loop then the direction of magnetic field lines inside the loop are again going into the table while outside the loop they are coming out of the table.
Question:
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is (a) towards south (b) towards east (c) downward (d) upward
Solution:
(d) Upward
Here, the positively-charged particle (alpha-particle) projected towards west, so the direction of current is towards west. The deflection is towards the north.


Let us use left hand Flemings rule: Adjust center finger towards west (I) and thumb towards north (EMF) then our forefinger will point in upward direction (MF)

03 March 2014

CBSE VIII Reproduction in plants and animals practice notes study

Microbes, plants, animals all need to grow up to an extent when they are able to perpetuate their own species. Thus, the species lives on from one generation to the next with the help of the life process called reproduction.

When two individuals are involved in reproduction, it is termed sexual reproduction.

When only one individual is involved in reproduction, it is termed asexual reproduction.

Binary fission is a kind of asexual reproduction in which a cell may divide to give rise to two individuals and lose its own identity . Binary fission that takes place in amoeba and bacteria

Budding is kinds of asexual reproduction in which bud develops on the body detaches from the parent body and give rise to new individual. Example: yeast, sponges and hydra.

Spore formation is kind of asexual reproduction in which new individual arises when globular structure known as   sporangia, which contains spores burst. Example: fungus, moss and fern.

Vegetative Propagation is a method of producing new plants from the vegetative parts of the plant .

Cutting: A piece of branch is cut and embedded in the soil. Roots form and a new plant results.

Layering: A branch of the plant is laid on the ground and a portion is embedded in the soil. This part strikes root and gives rise to new plant.

Grafting: The lower part of the stem or scion is cut in a wedge, The shoot of the plant to be used as a stock is cut off. The stem is slit vertically and the scion is inserted into the stock and tied with a tape.

Tissue culture :The process of formation of new plants with the help of a small tissue removed from a growing tip of a plant in a favourable medium(culture solution) is call tissue culture

Cloning: Cloning is the creation of an organism that is an exact genetic copy of another. The sheep Dolly is the first colon. Her mother’s udder cell nucleus was transferred into the egg of a “surrogate mother”, after removing the nucleus. Dolly’s mother provided her genes while the surrogate mother provided the womb for Dolly to develop from an embryo to a full fledged individual.

« Why is binary fission considered to be an asexual form of reproduction?  Ths is because it involve single parent.


Sexual reproduction in flowering plants occurs with the help of flower.  

Stamens (Androecium) which produce pollen are the male part. Pollen grains contain male sex cells. There may be several stamens in each flower. Each stamen (Androecium) has two parts. The upper part is known as anther which produce  pollen. It is held on the lower part called filament.

The pistil (Gynoecium) is the female part and its basal part is the ovary produce eggs or ovules called  female sex cells. The parts of the pistil are the stigma, style and ovary.

If  flower of plant bears both male and female parts. They are termed bisexual or hermaphrodites.

In some plants there are male flowers with only androecium and female flowers bearing only gynoecium. They are unisexual.  

Several agents like the wind, water, and insects. transfer pollen grain from anther to the stigma of a flower called pollination.

When pollen is brought on the stigma of the pistil reaches the ovule as pollen tube pushes through the pistil get fertilized.

The fertilized ovules develop into seeds which are capable of germinating into seedlings and new plants

« What will happen if the pistil of the flower is removed?  
 If the pistil of the flower, which is the female portion of the flower, is removed the flower would no longer be able to produce seed

Hydroponics: It is a method of growing plants using mineral nutrient solutions, in water, without soil.

In all animals, the female produces eggs within ovaries and the male produces sperms within testes.
An egg and a sperm fuse to form the zygote and takes place in the fallopian tube (the oviduct) which then develops into the embryo and the embryo into a full-fledged individual.

If fusion or fertilization takes place inside the mother’s body. They are termed viviparous. Animals that lay eggs include fish, frog, reptiles and birds and are thus called oviparous. if both female and male sex organs are in the same individual. Such individuals are termed hermaphrodite.

An embryo obtains nutrition for growth and development its body parts from mother’s blood through placenta. The embryo attached to the wall of uterus by placenta.

The close attachment of the embryo with the walls of uterus is called implantation.

A special tissue between the uterus wall and the embryo (foetus) that fulfils the nutritional, respiratory and excretory needs of the foetus from mother's body is called placenta.

The function of amniotic fluid is to protect the foetus against temperature changes and mechanical shocks.

The development of the foetus inside the uterus till birth is called gestation.

The birth of a fully developed foetus after the completion of gestation period is called parturition.

The embryo continues to develop in the uterus body parts such as hands, legs, head, eyes, ears, etc.
The stage of the embryo in which all the body parts can be identified is called a foetus . When the  development of the foetus is complete, the mother gives birth to the baby.

While in the womb, the baby floats in the amniotic fluid. The function of amniotic fluid is to protect the foetus against temperature changes and mechanical shocks.

Metamorphosis is the process of the transformation of larva into an adult through drastic change. For example  pupa into adult butterfly. Metamorphosis does not occur in viviparous animals because the young one resembles the adult at the time of birth.

In the hen, new individual hens [chick] develop from hen’s egg in about 3 weeks. He provides sufficient warmth to the egg to develop by sitting over it. This is called brooding. 


VIII  Reproduction in Animals    
Reproduction in Animals  [E-NOTES]
CBSE Test Paper  [solved question]
CBSE Worksheet for practice
Reproduction & Endocrine [solved]