Question

A condenser has two conducting plates of radius 10 cm separated by a distance of 5 mm. It is charged with a constant current of 0.15 A. The magnetic field at a point 2 cm from the axis in the gap is

• A. $6\times {10}^{-8}T$
• B. $3\times {10}^{-8}T$
• C. $6\times {10}^{-6}T$
• D. $3\times {10}^{-6}T$

Answer 1

Answer: (A)

$6\times {10}^{-8}T$

Given:

Radius, R =10 cm = 0.1m

Current, I=0.15 A

Distance ,r =2cm= 0.02m

Solution:

Magnetic field, B $=\frac{U_0\times I\times r}{2\times \frac{22}{7}\times R^2}$

$\Rightarrow B=\frac{4\times \frac{22}{7}\times {10}^{-7}\times 0.15\times 0.02}{2\times \frac{22}{7}\times {0.1}^2}$

$\Rightarrow B=6\times {10}^{-8}T$

Hence, correct option is A.