Question

A circular loop of radius ' \(r\) ' of conducting wire connected with a voltage source of zero internal resistance produces a magnetic field 'B' at its centre. If instead, a circular loop of radius ' \(2 r\) ', made of same material, having the same cross section is connected to the same voltage source, what will be the magnetic field at its centre ?
(A) \(\frac{B}{2}\)
(B) \(\frac{B}{4}\)
(C) \(2 B\)
(D) \(B\)

Answer 1

Ans: (B)
$$
\begin{aligned}
\text { }: & B=\frac{\mu_{0} I}{2 r}, \quad B^{\prime}=\frac{\mu_{0} I^{\prime}}{2.2 r}, \quad I=\frac{V}{R}, I^{\prime}=\frac{V}{2 R}=\frac{I}{2} \\
B^{\prime} &=\frac{\mu_{0} I^{\prime}}{4 \times 2 r}=\frac{B}{4}
\end{aligned}
$$

Answer 2

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Answer 3

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