Question

The magnetic flux through a coil perpendicular to its plane is varying according to the relation $\phi=\left(5 t^{3}+4 t+2 t-5\right)$ Weber. If the resistant of the coil is $5\, ohm$, then the induced current through the coil at $t =2\, \sec$ will be:

• A. 15.6 A
• B. 16.6 A
• C. 17.6 A
• D. 18.6 A

Answer 1

Answer: (A)

$\phi=5 t ^{3}+4 t ^{2}+2 t -5$
$| e |=\frac{ d \phi}{ dt }=15 t ^{2}+8 t +2$
At $t =2,| e |=15 \times 2^{2}+8 \times 2+2$
$\Rightarrow e =78\, V$
$\Rightarrow I =\frac{ e }{ R }=\frac{78}{5}=15.60$