A long straight wire carries a current of 35 A. What is the magnitude of the field B at a point 20 cm from the wire?

A straight wire carries a current of 3 A.Calculate the magnitude of the magnetic field at a point 15cm away from the wire. Draw a diagram to show tha direction of the magnetic field.

A circular coil of wire consisting of 100 turns, each of radius 8.0 cm carries a current of 0.40 A. What is the magnitude of the magnetic field B at the centre of the coil?