COMEDK · Physics · 21. Magnetic Effects of Current
The current through the circular coil is halved and the radius of the coil is doubled. If \(B_1\) and \(B_2\) are respectively the initial and final magnetic field strength, then:
- A \(B_2 = 4B_1\)
- B \(B_2 = \dfrac{B_1}{2}\)
- C \(B_2 = 2B_1\)
- D \(B_2 = \dfrac{B_1}{4}\)
Answer & Solution
Correct Answer
(D) \(B_2 = \dfrac{B_1}{4}\)
Step-by-step Solution
Detailed explanation
The magnetic field at the center of a circular coil is given by \(B = \dfrac{\mu_0 I}{2R}\). Initial magnetic field is \(B_1 = \dfrac{\mu_0 I}{2R}\). The current is halved, so \(I' = \dfrac{I}{2}\). The radius is doubled, so \(R' = 2R\). Final magnetic field is…
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