With the help of which law or rule can the direction of a magnetic field be known?

If you strike a sharp edge of a metallic knife against the north pole of a bar magnet,it will induce a north pole.

What is the frequency of $220 \ V$ $DC$ voltage? (In $Hz$)

The magnetic field produced by a straight current-carrying conductor is in the form of concentric circles.

Draw an appropriate schematic diagram showing common domestic circuits and discuss the importance of a fuse. Why is it that a burnt-out fuse should be replaced by another fuse of identical rating?

Normally,a red colour cable is used for the live wire in domestic electrical circuits.