Question

If the current in a coil of inductance $10,mH$ is increased from $1,A$ to $5,A$ in $0.2,s$, then the emf produced in it is

• A. $0.1,V$
• B. $0.3,V$
• C. $0.5,V$
• D. $0.4,V$
• E. $0.2,V$

Hint:

Physics Tip: Induced emf increases when current changes faster. Larger $\Delta I$ or smaller time gives higher emf.

Answer 1

Answer: (E)

Concept:
Self-induced emf in an inductor: $$e=L\frac{dI}{dt}$$ where $L$ is inductance.
Step 1: Convert units.
$$L=10,mH=10\times10^{-3}=0.01,H$$ Change in current: $$\Delta I = 5-1=4A$$ Time: $$\Delta t=0.2s$$
Step 2: Apply formula.
$$e=L\frac{\Delta I}{\Delta t}$$ $$=0.01\times\frac{4}{0.2}$$ $$=0.01\times20$$ $$=0.2V$$
Step 3: Final answer.
Hence induced emf is $0.2V$. Therefore option (E). :contentReference[oaicite:1]{index=1}