Given that two identical coils, one of copper and another of aluminium are rotated with the same angular speed in an external magnetic field, which of the following statements is true?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Induced emf will be same in both the coils whereas induced current will be more in copper coil.
For a coil rotating in a magnetic field the induced emf is
\( \displaystyle \varepsilon = NBA\omega\sin\omega t \)
It depends only on the number of turns, the field, the area and the angular speed, not on the material of the wire. The two coils are identical in shape and rotate at the same \( \omega \), so the emf is the same in both.
The current is \( I = \varepsilon/R \). Copper has a lower resistivity than aluminium, so the copper coil has the smaller resistance and carries the larger current.