Question

Find the odd one out:
(i). Voltmeter, ammeter, galvanometer, thermometer
(ii). Loudspeaker, bar magnet, electric motor, microphone

Answer 1

Part (i):
A voltmeter is a device that is used to measure the electric potential across two points in an electric circuit.
An ammeter is a device that is used to measure the current flowing in an electric circuit.
A galvanometer is a device that is used to detect the presence of current (and its direction provided current is present) in an electric circuit.
A thermometer is a device that is used to measure the temperature of an object.

Part (ii):
A loudspeaker is a device which utilizes a magnet to convert electric signals into sound waves. Additionally, a loudspeaker also amplifies sound.
Bar Magnet is nothing but a magnet in a cuboidal shape with its poles at both the ends.
An electric motor is a machine which utilizes a rotating coil in a magnetic field to convert electrical energy into mechanical energy.
The microphone is a device which utilizes a magnet to convert sound waves into electrical signals.

Complete step by step solution: Part (i):
Here we can observe that Voltmeter, Ammeter and Galvanometer are devices which are related to electrical circuits (Since they measure voltage or current). Whereas, Thermometer is a device related to Temperature (Since it measures temperature of bodies).

Hence Thermometer is the odd one out.

Part (ii):
Here we can observe that a loudspeaker, electric motor and microphone are devices / machines which utilize a magnet for operation. Whereas a bar magnet is neither a device nor a machine. It is just a magnet.

Hence Bar Magnet is the odd one out.

Note: In the second part, most students have no idea that a microphone utilizes a magnet. Hence they incorrectly mark the microphone as the odd one.