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Physics Practical Class 12 - To Determine the Internal Resistance of a Given Primary Cell Using a Potentiometer. Viva Questions with Answers

1) What is Electromotive Force?

The electric potential generated by either changing the magnetic field or electrochemical cell is known as electromotive force. It is commonly known as EMF.

2) Define potential difference.

The energy that degenerates as the unit charge passes through the components is known as the potential difference. During the measurement, the potential difference depends on the resistance between the two points.

3) What is the difference between EMF and terminal voltage?

Following are the main difference between EMF and terminal voltage:

  • When the circuit is on, the potential difference across the terminals of a load is known as terminal voltage. On the other hand, the maximum potential difference that is delivered by the battery when there is no flow of current is known as EMF.
  • A potentiometer is used for measuring the EMF, whereas a voltmeter is used for measuring the terminal voltage.

4) What is a Potentiometer?

A potentiometer is basically a resistor with three terminals that forms a variable voltage separator by having either descending or revolving contact. A potentiometer should have only two terminals with one end and the wiper in order to use it as a rheostat or variable resistor.

5) Write two applications of a potentiometer.

  • Audio control: For changing the loudness and other audio related signals, both rotary and linear potentiometers are used to control audio equipment.
  • Television: To control the picture brightness, contrast and colour response, potentiometers are used.

6) What is electrical resistance?

Electrical resistance is the hindrance provided by a material in the flow of current; it is the physical property of a substance which allows it to oppose the flow of electrons, that is, current. Resistance is inversely proportional to the cross-sectional area of the material and directly proportional to the temperature and length of the material.

7) What is direct current?

Direct current is the current whose direction remains the same. From a region of high electron density to a region of low electron density, the flow of electrons in a direct current is constant. Direct current is widely used in applications that involve a battery and many household appliances.

8) Why is Ohm’s law not applicable to semiconductors?

The semiconductors are nonlinear devices, and this is the reason why Ohm’s law is not applicable to semiconductors. This means that for variations in voltage, the ratio of voltage to current doesn’t remain constant.

9) When does Ohm’s law fail?

When semiconductors and unilateral devices such as diodes come into play, Ohm’s law fails to give the desired result because, in these materials, the physical conditions, such as temperature or pressure, do not remain constant.

10) What is a Wheatstone bridge?

A Wheatstone bridge is a particular type of electrical circuit that is used in measuring the unknown electrical resistance of the circuit by balancing the two legs of the bridge circuit, where the unknown component includes one of its legs.

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