Question

For a moving coil galvanometer, the deflection in the coil is $005$ rad when a current of $10 \,mA$ is field is $0,01 \,T$ and the number of turns in the coil is $200$ , the area of each tum (in $cm ^2$ ) is :

• A. $2.0$
• B. $1.0$
• C. $1.5$
• D. $0.5$

Answer 1

The Correct Option is B

The correct answer is (B) : 1.0
$\tau =K\theta$
$NiAB=K\theta$
$A=\frac{K\theta }{NiB}=\frac{4\times 10^{-5}\times 0.05}{200\times 10\times 10^{-3}\times 0.01}$
On solving $A=10^{-4}{m}^2=1c{m}^2$

Answer 2

The following provides the torque operating on the coil: \[ \tau = K\theta. \] The magnetic torque is: \[ \tau = NiAB. \] Comparing the two: \[ NiAB = K\theta. \] Rearranging for \( A \): \[ A = \frac{K\theta}{NiB}. \] Substituting the given values: \[ A = \frac{(4 \times 10^{-5}) \cdot (0.05)}{200 \cdot (10 \times 10^{-3}) \cdot (0.01)}. \] Simplifying: \[ A = 10^{-4} \, \text{m}^2 = 1 \, \text{cm}^2. \] Final Answer: \[ \boxed{1.0 \, \text{cm}^2} \]