Question

The network shown in the figure is part of a complete circuit. If at a certain instant, the current $i$ is $5\text{A}$ and decreasing at a rate of ${10}^3{As}^{-1}$ then potential difference between $A$ and $B$ ($V_B-V_A$ ) is equal to

• A. $20V$
• B. $15V$
• C. $10V$
• D. $5V$

Answer 1

The correct option is B $15V$

Since
$\frac{di}{dt}=-{10}^3{As}^{-1}$, the inductor opposes it by inducing a current in the same direction as $i$.

$L\frac{di}{dt}=5\times {10}^{-3}\times {10}^3=5\text{V}$
We have,

Using Kirchhoffs voltage law from $A$ to $B$,
$V_A-5+15+5=V_B$
$\Rightarrow V_B-V_A=15\text{V}$