PHYSICS [3 Mark Question Answer]

Materials that allow electric current to flow through them easily are called conductors. Such materials offer very low resistance to the flow of electric current through them. Materials that do not allow electric current to flow through them are called bad conductors of electricity or insulators. Such materials offer high resistance to the flow of electric current through them.

When connected in series :

• All appliances work simultaneously when switch is closed (turned on) and they stop working when switch is open (off).
• If any one of the appliances is out of order, all others stop working.
• Appliances do not work to their full capacity.

When connected in parallel :

• Each appliance will receive same voltage.
• Each appliance works independently.
• If one is out of order, other continue working.

It is possible to recharge a car battery because car batteries consists of secondary cells connected together. Each cell has a plate of lead and another of lead oxide dipped in the acid. Secondary cells can be recharged by passing an electric current through them. Because the reaction in these cells are reversible.

The cells that can be used only once are called primary cells. When the chemicals are used up completely, the cell becomes dead, and cannot be reused. The most common primary electric , cell is the simple dry cell that is used in torches, transistors, radios, clocks, wrist watches, calculators and TV remotes.

Properties of a magnet:
(a) A magnet is able to attract magnetic materials.
(b) Like poles of a magnet repel each other and unlike poles attract each other.
(c) A freely suspended magnet always rests in the north- south direction.
(d) The poles of a magnet cannot exist independently, they always occur together.

A freely suspended magnet always rests in the north-south direction. This property is called the directive property of magnets. The end of the magnet that points towards the geographical North Pole is called the north pole (N) of the magnet, whereas the end pointing towards the geographical South Pole is called the south pole (S) of the magnet.