Magnetic Field Due to Circular Current Carrying Wire

Practice Questions:

Question 1: easy

A length of wire carries a steady current. It is bent first to form a circular plane coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre caused by the same current is :

1. a quarter of its first value

2. unaltered

3. four times of its first value

4. half of its first value

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Question 2: easy

Consider two long solenoids \( A \) and \( B \) having length \( 2L \) and \( 3L \) and number of loop as \( N \) and \( 2N \) respectively. If both have same current then ratio of magnetic field inside \( A \) to that of the \( B \) will be

1. \( \frac{3}{4} \)

2. \( \frac{3}{2} \)

3. \( 1 \)

4. \( \frac{1}{2} \)

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The magnetic field inside a solenoid is given by \( B = \mu_0 \frac{N}{L} I \). Calculating the ratio: \( \frac{B_A}{B_B} = \frac{N_A / L_A}{N_B / L_B} = \frac{N / 2L}{2N / 3L} = \frac{3}{4} \).

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