(i) Battery
(ii) Fuse
(ill) Torch
(iv) Switch

No, a geyser and a television set require different amount of current. Therefore the fuse used in these will be of different ratings.

The child may put his/her fingers into the socket and he/she may get an electric shock which could be fatal.

MCBs (Miniature circuit breakers) are switches which automatically turn off when current in a circuit exceeds the safe limit. We turn them on and the circuit is once again complete

There are following two reasons of excessive currents in our houses:
(i) Direct touching of wires : This may happen if the insulation on the wires has come off due to wear and tear. This may cause a short circuit.
(ii) Connection of many devices to a single socket. This may overload in the circuit

When the switch is in ON position then the circuit from the positive terminal of battery to the negative terminal is complete. The circuit is then said to be closed and the current flows throughout the circuit instantly and bulb starts glowing

We should never touch a lighted electric bulb connected to the mains. It may be very hot and our hand may get burnt badly. In the same way, we do not experiment with the electric supply from the mains or a generator or an inverter. It may cause an electric shock.

When the switch is in off position then the circuit from the positive terminal of battery to the negative terminal is not complete. The circuit is then said to be opened and current does not flow throughout the circuit and bulb does not glow.

Battery is a combination of two or more cells. This can be constructed by placing cells properly on cell holder such that the positive terminal of one cell is connected to the negative terminal of the other. A piece of wire is connected to each of the two metal clips on the cell holder

The lighted bulb connected to main supply should not be touched by our hand directly, as a lighted bulb can be very hot and can burn our hand as well.

The value of the current in a circuit increases heavily at the time of short circuit.

No, the bulb does not glow when the circuit is opened. The bulb glows only when the circuit is closed.

When the current through the coil stops flowing, the coil does not remain an electromagnet.

Some of the electric appliances where the heating effect of the electric current is used are electric heater, geyser, micro-oven, room heater, boiler, etc.