Question

A compass needle placed just above a wire in which electrons are moving towards the west, will point towards

• A. East
• B. West
• C. North
• D. South

Answer 1

The correct option is D

South

Right-hand thumb rule:

1. The right-hand thumb rule is generally used to find out the direction of the current if the direction of the magnetic field due to the current is known or vice-versa.
2. To find out the direction of the magnetic field, we need to point the thumb of our right hand in the direction of the current.
3. Then, we need to curl the remaining fingers.
4. The direction of the curled fingers would give the direction of the magnetic field.

Explanation:

1. As electrons are moving toward the west, the current equivalently moves towards the east.
2. From the figure, we can see, by the right-hand thumb rule, when the current is in the direction of the thumb, i.e. the east direction, the folded fingers indicate the magnetic field.
3. Here the curled fingers show that the magnetic field points in the south direction.
4. This is the same direction as that of the earth's magnetic field.
5. Hence, the compass needle will point in the south direction.

Hence, option D is correct.