Question

A power line lies along the east-west direction and carries a current of 10 ampere . The force per metre due to the earth's magnetic field of ${10}^{-4}$ tesla is:

• A. ${10}^{-5}$ N
• B. ${10}^{-4}$ N
• C. ${10}^{-3}$ N
• D. ${10}^{-2}$N

Answer 1

The correct option is C ${10}^{-3}$ N

The correct option is C.

Given,

$current=10ampere$

The magnetic field of ${10}^{-4}tesla$

$F=B\times I\times L\times sinA$

Where, B is the magnetic field, I is the current,L is the length of wire and A is the angle between the magnetic field and the current flow.

Now,

$A={90}^0$ as the south-westward direction which is perpendicula to the earth magnetic field.

$L=1$

Thus the required force,

$F=B\times I=0.001\times 10={10}^{-3}N$