Why does a compass needle get deflected?
Compass needle get deflected when brought near magnet due to the force of the magnet.
The lines along which the iron fillings align themselves represent magnetic lines of force.
Magnetic field is a quantity that has both magnitude and direction. The direction of the magnetic field is taken to be the direction in which a north pole of the compass needle moves inside it.
The field lines emerge from the north pole and merge at the south pole out side magnet.Inside the magnet, the direction of field lines is from its south pole to its north pole. Thus the magnetic field lines are closed curves. This is why no two field-lines are found to cross each other.
Magnetic field due to current carrying conductor
The magnitude of the magnetic field produced at a given point increases as the current through the wire
The concentric circles representing the magnetic field around a current-carrying straight wire become
larger and larger as we move away from it.
Magnetic field due to current carrying circular loop:
We know that the magnetic field produced by a current- carrying straight wire depends inversely on the distance.
We know that the magnetic field produced by a current- carrying conductor at a given point, depends directly on the current passing through it.
Therefore, if there is a circular coil having n turns, the field produced is n times as large as produced by a single turn. This is because the current in each circular turn has the same direction, and the field due to each turn then just adds up.
Questions Bank Magnetic effects of electric current
solved questions -Magnetic effects of electric current
NCERT Magnetic Effects of Currents SOLVED QUESTIONS
ncert solution Magnetic Effects of Electric Current
Magnet A substance which has the property of attracting other substances like iron filings and points in the north south direction when suspended freely is called a magnet.
Magnetic field The space around a magnet in which the force of attraction and repulsion due to it can be detected is called the magnetic field.
Magnetic field lines The curved paths along which the north pole of the compass needle moves in a magnetic field are called magnetic field lines. Magnetic field lines are used to represent a magnetic field.
Properties of magnetic field lines
The magnetic field lines never intersect each other because if they do so it means that at that point the compass needle would point towards two directions which is not possible.
They emerge at North Pole and merge at South Pole.
They are crowded near the poles and are far apart near the middle.
These are directed from North Pole to South Pole outside the magnet and from south to North Pole inside the magnet.
Compass needle A compass needle is a small bar magnet whose ends always point towards north south direction. The end pointing towards north is called North Pole and the end pointing towards south is called South Pole.
Magnetic field due to a current carrying straight wire The straight current carrying conductor produces a magnetic field around it in the form of concentric circular field lines with the conductor at the centre.
Factors affecting strength of magnetic field around a current carrying straight conductor. Strength of magnetic field is directly proportional to the current passing through the conductor and inversely proportional to the distance from the conductor. ( B a I and B a 1/r )
Right hand thumb rule or Maxwell’s clockwise rule If we hold a straight wire in our right hand, and if the thumb represents the direction of current then the fingers represent the direction of magnetic field lines.
Magnetic field due to current carrying circular loop or coil When the current is passed through circular loop or coil, the lines of force are circular near the wire but straight and parallel near the centre of loop or coil. Factors affecting magnetic field due to current carrying circular loop or coil.
Magnetic field due to current carrying circular loop at its centre is–
Directly proportional to the current passing through it.
Inversely proportional to the radius of loop.
Magnetic field due to current in a solenoid The Magnetic field due to current carrying solenoid is similar to the magnetic field produced by a bar magnet. The ends of the solenoid act as North Pole and South Pole. The field lines inside the solenoid are in the form of straight parallel lines.
Factors affecting Magnetic field due to current in a solenoid
1. Magnetic field is directly proportional to the number of turns in the coil.
2. It is directly proportional to the current passing through it.
3. It is inversely proportional to the length of air gaps between the poles.
4. It depends on the nature of the core material used in the solenoid. Electromagnet.
An electromagnet consists of a long coil of insulated copper wire wrapped around a soft iron core. It is a temporary magnet as it works as long as current is passed through it. Factors affecting the strength of magnetic field of an electromagnet
The strength of magnetic field of an electromagnet is –
1. Directly proportional to the number of turns.
2. Directly proportional to the current flowing through it.
3. Inversely proportional to the length of air gaps between the poles.
Uses of electromagnet
1. They are used in electrical devices such as electric bell, electric fan, motor, and generator.
2. They are used for lifting and transporting large mass of iron.
3. They are used in medical practices for removing pieces of iron from wound and used in MRI.
A permanent magnet is made from steel alloys like carbon steel, chromium steel, cobalt steel, etc. They are weaker than electromagnets and their strength and polarity cannot be changed. Force on a current carrying conductor in a magnetic field.
A current carrying conductor placed in a magnetic field experi- ences a force due to the interaction between ---
b. External magnetic field in which conductor is placed.
Force on a current carrying conductor in a magnetic field
a. Magnetic field due to current carrying conductor and
b. External magnetic field in which conductor is placed.
Flemming’s Left Hand Rule
Principle of electric motor
Flemming’s Right Hand Rule.
Principle of electric generator When a coil of copper wire is moved in a strong magnetic field, a current is induced in the coil.
Steps to avoid overloading
Short circuiting When the live wire and neutral wire come into direct contact, a large amount of current flows through the circuit due to very small resistance, this is called short circuiting. The heat produced during short circuiting is so high that it may cause fire.