A vertical wire carries a current straight down. To the east of this wire, the magnetic field points:

• A: eastwards

• B: downwards

• C: southwards

• D: northwards

Use the right-hand rule. Point your thumb down. Your fingers curl toward the south when you look on the east side of the wire. Option (c) is the answer.

The direction of field lines is identified by using the right-hand thumb rule.