Question

I. Two students make a solenoid each with the same length but the number of turns is in the ratio of 1:4. If they carry the same current, the ratio of the magnetic field a] 1:2 b] 1:4 c] 3:2 d] 4:1 II. A coil of insulated copper wire is connected to a galvanometer forming a loop and a magnet is ------ 1. Held stationary 2. Moved towards along its axis 3. Moved away along its axis. Deflection in galvanometer is observed in --------------- a] (1) only b] (1) and (2) only c] (2) and (3) only d] (1), (2) and (3)

Answer 1

Answer:

1.4:1

2.held statioary

3. (1)(2)(3)

Answer 2

Answer:

1.] b]1:4

2.] c.] (2) and (3)

Explanation:

1.] Magnetic field in a solenoid carrying current = $\mu_o n I$

where,  $n$ be number of turns per unit length in solenoids.

$I$ is current flowing through the circuit

Magnetic field in first loop = $B = \mu_o n_1 I$

Magnetic field in second loop = $B = \mu_o n_2 I$

Ratio of magnetic fields = $\frac{B_1}{B_2}=\frac{\mu_o n_1 I}{\mu_o n_2 I}=\frac{n_1}{n_2} = \frac{1}{4}=1:4$

2.] In 2. and 3. option, when copper wire connected to galvanometer is moved either way (toward or away from axis); then only the flux linked to the circuit will change.

From Faraday's law, Any change in the magnetic environment of a coil of wire will cause an emf to be induced in the coil.

This in turn will produce an emf in the circuit and then a current will flow in the circuit. This will produce deflection in the galvanometer.

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