Question

Name the device that uses an electromagnet
A. Electric bell
B. Barometer
C. Lactometer
D. All the above

Answer 1

Hint: Electric bell is a device that uses electromagnet property. When current passes through a circuit, a coil attached to the circuit produces a magnetic field and acts as a magnet. Because of magnetism produced in coil, a gong gets strike. Electromagnet is a magnet which is created by passing current through a coil or rod. Current requires electricity then only a magnet can be created.

Complete step-by-step answer:
An electromagnet is a type of magnet in which magnetic field is produced when change in electric current is possible or when current will be on. If current will flow then the magnetic field will disappear. In electromagnet, coil is used to produce magnetic fields. Coil is basically closely spaced turns of wire in large numbers which is responsible for producing magnetic fields. The wires are usually wound around a magnetic core which must be made up of ferromagnetic or ferromagnetic material like iron. This magnetic core concentrates the magnetic flux. Magnetic flux is nothing but the number of magnetic lines passing through a given area. So more the lines will be magnetic flux and it makes the coil a more powerful magnet.
There are lots of advantages of electromagnet then a permanent magnet but the main advantage is if we control the amount of electric current in winding or coils, magnetic field B will quickly change.
The ball works on the principle of electromagnet. In an electric ball, a switch is present in the bell. If the switch is pressed the current flows through the circuit. The electromagnet that is coil is powered up and then a magnetic field is generated. After that hammer/striker moves and hits the gong. When the hammer is moved at that time the circuit breaks and the electromagnet gets unpowered. This causes the hammer to go back to its initial position because of spring present in the bell and circuit will close again.
Answer is (A) Electric bell

Note: Strength of electromagnet can be changed by changing the amount of current which flows through the coil. Barometer works on principle- It works on balancing the weight of mercury in a glass tube against atmospheric pressure.
Lactometer works on principle- It is used to check milk quality. It works on Archimedes’ principle.