Question

$P$ and $Q$ are two thin circular coils of same radius and subjected to the same rate of change of flux. The magnetic field is perpendicularly inwards to their plane and varrying with time. If coil $P$ is made of copper and $Q$ is made of iron, then the wrong statement is $\left({\rho }_{iron>{\rho }_{copper}}\right)$

• A. emf induced in the two is the same.
• B. the induced current in $P$ is more than that in $Q$.
• C. Resistance of two coils are different.
• D. the induced currents are the same in both the coils.

Answer 1

The correct option is D the induced currents are the same in both the coils.

Induced emf will be same for both the coils
${\epsilon }_P={\epsilon }_Q$
$\because \epsilon =-N\frac{d\varphi }{dt}\&\frac{d\varphi }{dt}$ is same for both coils.
However induced current in coils is,
$i=\frac{\epsilon }{R}$
$R_{\text{iron}}>R_{\text{copper}}$
Hence induced current in iron coil will be lesser.