PHYSICS [3 Mark Question Answer]

The space around the magnet where its influence can be experienced is known as magnetic field. This field is formed by the magnetic lines of force which run from the North pole to the South pole. These lines can be found to be maximum crowded at the two ends of the magnet which are the poles i.e. the North pole and the South pole.

Magnetic compass is a device that is used to locate the direction of a place. It always rests in a North-South direction. It is used in the navigators in ships, submarines, aeroplanes, etc.

Precautions to be taken beofre the circuit is switched on
Before the circuit is switched on, following precautions must be taken :

1. See that all the components of the circuit are properly connected.
2. See that the connection wire is tightly connected to each appliance or component.
3. Do not touch the switch or any component with wet hands.

Current always flows from +ve terminal to the -ve terminal of a cell.

The bulb will glow in circuit (D).
This is because copper is the best conductor of electricity as compared to aluminium. Silk is a non-conductor of electricity.

Conductors

1. Conductors are those subs¬tances which allow electricity to flow through them.
2. e.g. all metals, human body.

Insulators
Insulators are those which do not allow electricity to pass through them. –
e.g. wood, paper, glass.

Magnetic declination is the angle of the horizontal plane between the magnetic North and the geographic North (or true North). This angle is shown in figure by symbol θ.
The angle of declination is different at different places on the earth surface and it also changes at a place with time. The declination is taken positive if the magnetic North is towards the east of the true North as in figure and is negative if the magnetic north if towards the west of the true North.

Uses of electromagnet —

1. In electrical appliances such as electric bell, fan etc.
2. In lifting heavy loads of iron scrap.
3. To remove tiny particles of iron from the wound.
4. In loading furnaces with iron.
5. In separation of magnetic substances from the non-magnetic substances.

An electromagnet — An electromagnet is a temporary magnet which behaves as a magnet when electric current is passed through the insulated copper wire and loses its magnetism when current is stopped. It has a soft iron piece called the core with an insulated copper wire wound on it.