Magnetic Effects Of Current Question 7
Question 7 - 25 January - Shift 2
For a moving coil galvanometer, the deflection in the coil is $0.05 rad$ when a current of $10 mA$ is passed through it. If the torsional constant of suspension wire is $4.0 \times 10^{-5} Nm rad^{-1}$, the magnetic field is $0.01 T$ and the number of turns in the coil is 200 , the area of each turn (in $cm^{2}$ ) is :
(1) 2.0
(2) 1.0
(3) 1.5
(4) 0.5
Show Answer
Answer: (2)
Solution:
Formula: Moving coil galvanometer
$\tau=K \theta$
$NiAB=K \theta$
$A=\frac{K \theta}{NiB}=\frac{4 \times 10^{-5} \times 0.05}{200 \times 10 \times 10^{-3} \times 0.01}$
On solving $A=10^{-4} m^{2}=1 cm^{2}$
