Notes of Ch 14 Electric Current and its Effects Class 7th Science

What is electric current?

→ It is a flow of electrons through a conductor.

→ It flows through a wire, the wires gets heated. It is the heating effect of current.

Electronic component

→ It can be an element of an electric circuit that helps in its functioning.

• Electric circuit: It allows electricity to flow through it and is used to provide electricity for various purposes such as running electric motors providing electricity to a bulb or a fan, generating heat.

• Battery: Battery is a combination of two or more cells. The positive terminal of one cell is connected to the negative terminal of another cell.

Electric circuit

→ It helps the symbols that are used for representing the electronic components.

Types of circuit

→ There are two types of circuit:

(i) Open circuit: When the key is opened or switched off the circuit is said to be an open circuit.

(ii) Close circuit: When the key is closed or switched on the circuit is said to be a closed circuit.

Heating effect of electric current

→ Wire gets heated up when an electric current passes through it.

• The heat produced in the wire depends upon the following factors:
(i) Length of wire
(ii) Material of wire
(iii) Thickness of wire

• Examples of appliances works on the heating effect of electric current:
(i) Iron
(ii) Electric heater
(iii) Electric stove
(iv Geysers

• Fuse: It prevent damage to electric circuit. It is act as a safety device.

• MCB: MCB stands for miniature circuit breakers. MCB is a switch which automatically turn off when current in a circuit exceeds the safe limit.

Magnetic effect of electric current

→ Passing of electric current through a wire it behaves like magnet. This is called magnetic effect of the electric current.

→ It is discovered by a scientist Hans Christian Oersted.

Electromagnet

→ It is a coil of wire wound on a soft iron core which is used to separate magnetic material from the junk.

→ It is formed because the magnetic effect of the electric current.

• Application of electromagnets:

→ Used in toys
→Used in electric bells
→ Used in all kinds of telecommunication equipment

Electric bell

→ In electric bell there is electromagnet is present in it.

→ It has a coil of wire wound around a piece of iron.

→ The iron strip with a hammer is kept close to the electromagnet and also there is a contact screw near the iron strip.

→ When iron strip is in contact with the screw the current flows through the coil and acts as electromagnet.

→ Then it pulled the strip and hammer at the end of the strip strikes the gong of the bell and produces sound.