False.
The representation of the electric current is 'I'.

False.
The Fuse wire melts whenever there is overload in the wiring.

False.
Electron flow is in the opposite direction to conventional current flow.

10^-6A

Ammeter.

Insulator

Metals

A. If both A and R are true and the R is correct explanation of A.

Batteries are a collection of one or more cells.

Wood, Glass, Plastic, Rubber are some examples of insulator.

Fuse is a safety device which is used in household wiring and in many appliances.

The speed of electric current is 6.242 x 10¹⁸ protons or electrons.

Electrical conductivity is the measure of a material's ability to conduct an electric current. It is commonly represented by the Greek letter σ(sigma). The S.I Unit of electrical conductivity is Siemens/meter(S/m).

The flow of electric charges constitute an electric current. An electric current is measured by the amount of electric charge moving per unit time at any point in the circuit

(i) Dry cells are normaly used in small devices such as remote control for T.V., torch, camera and toys.
A dry cells is a portable form of a leclanche cell. It consists of zinc vessel which acts as a negative electrode or anode the vessal contains a moist paste of saw dusts saturated with a solution of ammonium chloride and zinc chloride. The ammonium chloride acts as an electrolyte.
(ii) Electrolytes are substances that become ions in solution and acquire the capacity to conduct electricity.
(iii) The purpose of zinc chloride is to maintain the moistness of the paste being highly hygroscopic. The carbon rod covered with a brass cap is placed in the middle of vessel. It acts as positive electrode or cathode.
(iv) It is surrounded by a closely packed mixture of charcoal and manganese dioxide (MnO₂) in a muslin bag. Here MnO₂ acts as depolarizer. The zinc vessel is sealed at the top with pitch or shellac. A small hole is provided in it to allow the gases formed by the chemical action to escape. The chemical action inside the cell is the same as in leclanche cell

Telephone:
In telephones, a changing magnetic effect causes a thin sheet of metal (diaphragm) to vibrate. The diaphragm is made of a metal that can be attracted to magnets.
1) The diaphragm is attached to spring that is fixed to the earpiece.
2) When a current flows through the wires, the soft - iron bar becomes an electromagnet.
3) The diaphragm becomes attracted to the electromagnet
4) As the person on the other end of the line speaks, his voice cause the current in the circuit to change. This causes the diaphragm in the earpiece to vibrate, producing sound.

c) S2, S3 and S4 only

a) 4 A
PR + QR = RS
PR + 6A = 10A
PR = 10 - 6 = 4A