a. On what principle does an electric fuse work?

b. What is the frequency of A.C. in India? State one advantage of A.C over D.C.

a. An electric fuse works on the heating effect of electric current. When a current higher than the rating of the fuse passes through it, the fuse melts. As the fuse is connected in series to the household appliances just after the main switch, it disconnects all the appliances from the main switch by melting. In this way, a fuse protects the appliances from excess current.

b. The frequency of A.C. in India is 50 Hz. An alternating current is advantageous over DC for long range transmission of electricity because it can be transmitted over long distances without much loss of electric power as compared to direct current.