Chapter 11 · Question 2

Define potential difference and explain how a voltmeter is connected in a circuit. How much energy is given to each coulomb of charge passing through a 6 V battery?

Answer Revealed

Direct Answer:

Potential difference between two points is the work done in moving a unit charge from one point to the other. A voltmeter is always connected in parallel across the points between which the potential difference is to be measured. Each coulomb of charge passing through a 6 V battery receives 6 J of energy.

Simple Explanation

Potential difference is what pushes charge through a circuit — it is the work done per unit charge. A voltmeter measures this and must be connected in parallel, like attaching a pressure gauge to both sides of the pipe rather than cutting the pipe. For a 6 V battery, every coulomb of charge gets 6 joules of energy.

Exam-Ready Structure

Potential difference is a key concept that explains why charges move in a circuit: 1. The potential difference (V) between two points in an electric circuit carrying some current is defined as the work done (W) to move a unit positive charge (Q) from one point to the other. Mathematically,

V = W / Q

. 2. The SI unit of potential difference is the volt (V). One volt is the potential difference when 1 joule of work is done to move 1 coulomb of charge between two points (

1\ \text{V} = 1\ \text{J} / 1\ \text{C}

). 3. A cell or battery maintains a potential difference across its terminals and provides the 'push' that drives current through the circuit. 4. A voltmeter is an instrument used to measure the potential difference between two points in a circuit. It is always connected in parallel across the points between which the potential difference is to be measured. 5. For a 6 V battery: Using

V = W / Q

, the energy (work) given to each coulomb of charge is

W = V \times Q = 6\ \text{V} \times 1\ \text{C} = 6\ \text{J}

. So each coulomb receives 6 joules of energy.

Key Points

Potential difference $V = W / Q$ (work done per unit charge)
SI unit is volt (V); $1\ \text{V} = 1\ \text{J} / 1\ \text{C}$
A cell or battery maintains potential difference across a circuit
Voltmeter is always connected in parallel across the points being measured
Each coulomb of charge passing through a $6\ \text{V}$ battery receives $6\ \text{J}$ of energy

Common Mistakes

Connecting a voltmeter in series (it must be in parallel; series connection would block most of the current)
Confusing potential difference with current — potential difference is the cause, current is the effect

Define potential difference and explain how a voltmeter is connected in a circuit. How much energy is given to each coulomb of charge passing through a 6 V battery?