What deflection is produced in the galvanometer when there is a relative motion between the coil and the magnet?
Asked by Aditya Great | 7th Dec, 2014, 01:14: PM
The figure below shows a coil of few turns of conducting material insulated from one another. It is connected to a galvanometer.
When the magnet is held stationary, the galvanometer shows no deflection.
When the north pole of the magnet is brought towards the coil, the galvanometer shows a sudden deflection indicating that a current is induced in the coil.
The galvanometer deflection is temporary and it lasts as long as the bar magnet is in motion. There won't be any deflection when the bar magnet is held stationary anywhere.
When the magnet is moved away from the coil, the galvanometer shows deflection in the opposite direction indicating the direction of induced current in the reversed direction.
When the south pole of the bar magnet is moved towards or away from the coil, the deflection in the galvanometer will be opposite to that observed with the north pole for similar movements.
The deflection in the galvanometer will be larger when the magnet is pushed or pulled away from the coil faster.
This indicates that when there is a relative motion between the coil and the magnet a current gets induced in the coil. This current gets detected with the help of galvanometer.
This experiment shows that a current flows in the coil only when there is a relative motion between the coil and the magnet due to which the galvanometer connected with the coil shows deflection.The direction of deflection in a galvanometer is reversed if the direction of motion (or polarity of the magnet) is reversed.
This indicate that whenever there is a change in the magnetic flux linked with a coil, an emf is induced. The induced emf lasts so long as there is a change in the magnetic flux linked with the coil.This phenomenon in which an electric current is induced in a conductor because of a changing magnetic field is called electromagnetic induction.
Answered by Jyothi Nair | 8th Dec, 2014, 10:05: AM
- A magnetized needle of magnetic moment 4.6 × 10-2 JT-1 is placed at 30o with the direction of a uniform magnetic field of strength 4 × 10-2 T. a. What is the torque acting on it ?b. How much work is required for it to make a 120o angle with the magnetic field?
- A circular loop of radius a is placed in a diverging magnetic field B such that the angle between the normal to the plane of the loop and field anywhere on the loop is θ. Also, the magnetic field present is such that the lines cut the loop at 900. Derive an expression for the net force exerted by the field on the loop when a current i is made to flow through the loop.
- Derive an expression for the torque acting on a loop of N turns, area A, carrying current i, when held in a uniform magnetic field.
- A circular coil of 200 turns, radius 5 cm carries a current of 2.5 A. It is suspended vertically in a uniform horizontal magnetic field of 0.25 T, with the plane of the coil making an angle of 60o with the field lines. Calculate the magnitude of the torque that must be applied on it to prevent it from turning.
- State the underlying principle of working of a moving coil galvanometer. Write two reasons why a galvanometer cannot be used as such to measure current in a given circuit. Name any two factors on which the current sensitivity of a galvanometer depends.
- A circular coil of 200 turns and radius 10 cm is placed in a uniform magnetic field of 0.5 T, normal to the plane of the coil. If the current in the coil is 3.0 A, calculate the (a) Total torque on the coil (b) Total force on the coil (c) Average force on each electron in the coil due to the magnetic field Assume the area of cross-section of the wire to be 10-5m2 and the free electron density is 1029/m3.
- With the help of a neat and labelled diagram, explain the underlying principle and working of a moving coil galvanometer.
- What is meant by current sensitivity of a moving coil galvanometer? On what factors does it depend?In an exercise to increase the current sensitivity of a galvanometer by 25%, its resistance is also increased 1.5 time. How will the voltage sensitivity of the meter be affected?
- How the magnetic moment of an electron will change if we double the frequency of its revolution?
- A current loop is considered as a magnetic dipole. Explain.
Kindly Sign up for a personalised experience
- Ask Study Doubts
- Sample Papers
- Past Year Papers
- Textbook Solutions
Verify mobile number
Enter the OTP sent to your number