Chapter 24.1, Problem 6PP

(a)

To determine

The direction of the current in the wire.

Explanation of Solution

Introduction:

Right hand rule says that if one grabs the wire by the right hand such that the extended thumb points toward the direction of the convectional current, the fingers represent the direction of the magnetic field encircling the wire.

If the north pole of a compass points towards eastwhen placed above wire and wire carrying current is along north-south direction, then current must be flowing from south to north.

Conclusion:

Current flows from south to north in the wire.

(b)

To determine

The direction in which compass would point if placed beneath the wire.

Explanation of Solution

Introduction:

Right hand rule says that if one grabs the wire by the right hand such that the extended thumb points toward the direction of the convectional current, the fingers represent the direction of the magnetic field encircling the wire.

If the north pole of a compass points towards east when placed above wire, then when the compass is placed at the bottom (where there is south pole of the magnetic field due to wire carrying current), it would point towards west.

Conclusion:

The compass would point towards west.