Potential Difference MCQs Quiz | Class 10

This quiz for Class X Science (Code 086), part of Unit IV: Effects of Current, focuses on Potential Difference. It covers the definition, unit, and measurement concept. Attempt all 10 multiple-choice questions and then submit to see your score. You can also download a detailed answer PDF for revision.

Understanding Potential Difference: Key Concepts and Measurement

Potential difference is a fundamental concept in electricity, essential for understanding how electric circuits work and why current flows. It is often referred to as voltage and is the driving force behind the movement of charge.

1. Definition of Potential Difference

The electric potential difference between two points in an electric circuit is defined as the work done per unit charge in moving a positive test charge from one point to the other against the electric field. It essentially represents the energy provided to each unit of charge to move it between the two points.

Mathematically, potential difference (V) is given by:

V = W / Q

Where:

  • V is the potential difference
  • W is the work done
  • Q is the amount of charge moved

Think of it like water pressure: a difference in water pressure causes water to flow. Similarly, a potential difference (voltage) causes electric charge (current) to flow in a conductor.

2. Unit of Potential Difference

The SI unit of potential difference is the Volt (V), named after Alessandro Volta, who invented the electric battery.

One Volt is defined as the potential difference between two points in a current-carrying conductor when 1 Joule of work is done to move 1 Coulomb of charge from one point to the other.

So, 1 Volt = 1 Joule / 1 Coulomb (or 1 V = 1 J/C).

3. Measurement Concept

Potential difference is measured by an instrument called a voltmeter.

  • Connection: A voltmeter is always connected in parallel across the points between which the potential difference is to be measured. This is because it needs to measure the ‘drop’ in potential across a component, not the current flowing through it.
  • Resistance: An ideal voltmeter has infinitely high resistance. In practice, voltmeters have very high resistance to ensure they draw negligible current from the main circuit, thereby not altering the circuit’s original potential difference.
  • Symbol: In circuit diagrams, a voltmeter is represented by a circle with the letter ‘V’ inside it.

Quick Revision Points

  • Potential difference (voltage) is the work done per unit charge (V = W/Q).
  • Its SI unit is the Volt (V), equivalent to Joules per Coulomb (J/C).
  • Potential difference causes electric current to flow.
  • It is measured by a voltmeter.
  • A voltmeter is always connected in parallel across the component.
  • Voltmeters have very high resistance.

Table: Important Electrical SI Units

Quantity Symbol SI Unit Unit Symbol
Electric Charge Q Coulomb C
Electric Current I Ampere A
Potential Difference V Volt V
Work / Energy W / E Joule J
Resistance R Ohm Ω

Practice Questions

  1. Why is it necessary to have a potential difference for an electric current to flow in a circuit?
  2. If 30 Joules of work is done to move 5 Coulombs of charge from one point to another in an electric field, what is the potential difference between the two points?
  3. What is the main difference between electric potential and potential difference at a point?
  4. State the function of a voltmeter in an electrical circuit and how it should be connected.
  5. Name the unit that is equivalent to one Joule per Coulomb.