Question

A compass needle just above a wire in which electrons are moving towards the east will point:

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

Answer 1

The correct option is A

South

Explanation:

1. A compass magnetic needle rests in the north-south magnetic direction because the north magnetic pole is attracted to the earth's south pole.
2. The direction of electrons is opposite to the direction of flow of current. Therefore, when electrons move towards the east, current flows towards the west.
3. To find the direction toward which the compass needle will point, we need to find the direction of the magnetic field
4. We will apply the right-hand thumb rule, according to which the conducting wire is supposed to be held in the right hand.
5. The thumb shows the direction of the current; which in this case is west
6. The curled-up fingers show the direction of the magnetic field, which is perpendicular to the thumb
7. Thus, the magnetic field at a point just above the wire is towards the geometric north, which is in a direction opposite to the earth's magnetic field.
8. Hence, the compass points towards the south.

Hence, option (A) is the correct answer