USING ELECTRICITY – Class 7

MAGNETIC EFFECTS OF ELECTRICITY

Done byMrs. Aparna.S

MAGNETIC EFFECT OF ELECTRICITYConcept, Application and Uses

Hans Christian Oersted: In 1820, during a classroom demonstration of an experiment to his students, he noticed that a compass needle was deflected when an electric current was switched on nearby.He went on to study this effect further and discovered the connection between electricity & magnetism.

MAGNETIC EFFECT OF ELECTRICITY

MAGNETIC EFFECT OF ELECTRICITY – Oersted’s experiment

A compass needle can only be deflected by a magnet

When a current passes through a wire, it behaves like a magnet and has a magnetic effect around it

The area around it where the magnetic influence is felt is called the magnetic field caused due to electricity

MAGNETIC EFFECT OF ELECTRICITY – Oersted’s experiment and explanation

Thus, a coil of wire acts as a magnet when current flows through it

A solenoid is a cylindrical coil of wire that behaves like a bar magnet, with opposite poles at the ends, when a current flows in it

MAGNETIC EFFECT OF ELECTRICITY - Solenoid

Thus, a coil of wire acts as a magnet when current flows through it

If the coil is wound around a soft iron core such as an iron nail, the magnetic effect increases several times

An electromagnet is a coil wound around an iron core which acts as a magnet as long as an electric current flows through the coil

MAGNETIC EFFECT OF ELECTRICITY - Electromagnet

Useful properties of electromagnets:1. Increase in current increases the

strength of the electromagnet2. They are very strong temporary

electromagnets and become demagnetised as soon as the current is switched off

3. They come in varying shapes and sizes depending on their purpose

MAGNETIC EFFECT OF ELECTRICITY - Electromagnet

Application:1. Used to make electric motors that are

used in fans, refrigerators, AC units, electric bells, telegraph, telephones, loudspeakers, washing M/C s

2. Used to separate iron and steel from other materials in a metal scrapyard

3. Used in magnetic cranes for lifting and carrying heavy steel and cast iron articles in factories

MAGNETIC EFFECT OF ELECTRICITY - Electromagnet

The electric bell is a simple device that uses an electromagnet. It is used as a doorbell.

An electric bell consists of a battery, an electric switch, an electromagnet, an adjusting screw, a soft iron strip, a hammer and a gong.

MAGNETIC EFFECT OF ELECTRICITY – The Electric Bell

How it works?1. When you push the switch of a bell, the electric current flows

to the electromagnet.

2. The electromagnet attracts the soft iron strip. The hammer attached to the strip then hits the gong, causing a ring.

3. This movement breaks the circuit at the contact screw so that the current stops flowing and switches off the electromagnet.

MAGNETIC EFFECT OF ELECTRICITY – The Electric Bell

MAGNETIC EFFECT OF ELECTRICITY – The Electric Bell

How it works?4. The metal strip pulls back next so that contact is made

again at the contact screw and the circuit is complete and current flows again. Steps 1-4 keep repeating as long as the switch is on.

5. Thus, the hammer repeatedly strikes the gong producing a continuous ringing sound as long as the switch is pressed.