Have you seen the vehicle shown in fig? It is used to extract the steel, iron scrap from the dumped garbage in dumping yard of cities. You may feel that it’s a magnetic disc, but isn’t. It’s an electromagnet. It consist of metallic disc, to which source of electric energy is provided, so that it become magnet. We just need to hold the crane above the garbage and let all scrap stuck to the disc. When we want to remove the scrap from disc, disconnect the electricity supply; remove the scrap easily at desired location. Isn’t it strange? How the disc became magnet? And how suddenly it loses its magnetism too! Perform the simple activity given below.
- Take an iron nail and wrap insulated copper wire as shown in fig.
- Connect the terminals of wire to battery through tap key.
- Place few iron pins near the arrangement.
- Switch on the circuit by taping the key.
- Observe the pins which were kept near the iron nail. Now disconnect the circuit, and observe the pins again.
What did you recorded here? You must have noticed that the irons pins gets stuck to the nail with copper wire (shown in fig. above.) as soon as switch is ON and falls down immediately when switch is OFF. This happens due to one of the most phenomena produced due to electric current known as ‘Magnetic effect of electric current’.
This effect was first studied by Sir H.C.Oerstad in 1820. He observed that, when electric current flows through the metallic conductor, magnetic compass kept beside the wire starts deflecting. The deflection of the needle in compass increases due to increase in current. The direction of needle reverses due to reversing the direction of current. Hence Sir Oerstad concluded that when current flows through wire magnetic field is produced around the wire and thus the conducting wire behaves as a magnet. This phenomenon is known as magnetic effect of electric current. The phenomenon in which magnetic field produced around the conductor carrying current is called as magnetic effect of electric current.
The wire wrapped on a nail is taken termed as Coil, which behaves like a magnet when electric current flows through it. When the electric current is switched off, the coil loses its magnetism. Such coils can be called as electromagnets. The electromagnets can be made very strong as per requirement by changing value of current flowing through it. This phenomenon has very wide range of applications in our daily routine as well as in industries also.
Take a look on following applications.
- It is used in Electric bells and buzzers.
- It is used in MRI machine for scanning of body for particular diseases.
- It is used in industries for lifting heavy objects, scrap, cars etc.
- It is also used in loudspeakers, head phones etc.
Q. What do you mean by magnetic effect of electric current?
Ans: The phenomenon in which magnetic field produced around the conductor carrying current is called as magnetic effect of electric current.
Q. Who invented magnetic effect of electric current?
Ans: Sir H.C.Oerstad in 1820.
Q. On which factors the strength of magnetic field depends?
Ans: Magnetic field produced due to electric current depends upon 1. Current- Magnetic field increases with increase in current. 2. Distance- Magnetic field decreases with increase in a distance of coil from compass.
Q. What are electromagnets?
Ans: The wire wrapped on an object acts as electromagnet, which behaves like a magnet when electric current flows through it.