Question

A coil of effective area \(3\) m\(^2\) is placed at right angles to a magnetic field of induction \(0.05\) Wb/m\(^2\). If the field is decreased to \(20\%\) of its original value in \(10\) second, the e.m.f. induced in the coil will be

• A. \(15\) mV
• B. \(12\) mV
• C. \(10\) mV
• D. \(5\) mV

Hint:

emf = A times change in B divided by time.

Answer 1

The Correct Option is B

Step 1: Flux values:
Initial flux $= 0.05\times3 = 0.15$ Wb. Final flux $= 0.01\times3 = 0.03$ Wb.

Step 2: Change in flux:
$0.15 - 0.03 = 0.12$ Wb.

Step 3: Rate:
$\frac{0.12}{10} = 0.012$ V, which is 12 mV.

Final Answer:
The emf is 12 mV, option (B). \[ \boxed{12\text{ mV}} \]