MHT CET · Physics · Magnetic Effects of Current
A current passing through a circular coil of two turns produces a magnetic field \(B\) as its centre. The coil is then rewound so as to have four turns and the same current is passed through it. The magnetic field at its centre now is
- A \(2 B\)
- B \(B / 2\)
- C \(B / 4\)
- D \(4 B\)
Answer & Solution
Correct Answer
(A) \(2 B\)
Step-by-step Solution
Detailed explanation
According to questions
\(
\begin{array}{l}
2 \times 2 \pi_{1}=4 \times 2 \pi r_{2} \\
r_{1}=2 r_{2} \\
\text { and } \quad B_{1}=\frac{\mu_{0} 2 \pi I}{4 \pi r_{1}} \\
B_{2}=\frac{\mu_{0} 2 \pi I}{4 \pi r_{2}}=\frac{\mu_{0} 2 \pi I}{4 \pi r_{1} / 2} \\
B_{2}=2 B_{1}
\end{array}
\)
\(
\begin{array}{l}
2 \times 2 \pi_{1}=4 \times 2 \pi r_{2} \\
r_{1}=2 r_{2} \\
\text { and } \quad B_{1}=\frac{\mu_{0} 2 \pi I}{4 \pi r_{1}} \\
B_{2}=\frac{\mu_{0} 2 \pi I}{4 \pi r_{2}}=\frac{\mu_{0} 2 \pi I}{4 \pi r_{1} / 2} \\
B_{2}=2 B_{1}
\end{array}
\)
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