What produces magnetism in the human body?

Why is it safe for birds to sit on naked power lines fixed atop tall electric poles?

A domestic lighting circuit has a fuse of 5 A. If the mains supply is at 230 V, calculate the maximum number of 36 W tube-lights that can be safely used in this circuit.

Name one medical technique which is based on magnetism produced in human body. For what purpose is this technique used?

Name two human body organs where magnetism produced is significant.