Electromotive Force and Potential Difference

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Questions and Answers

What is the main function of a voltmeter?

To check resistance in a component
To measure potential difference (correct)
To measure current in a circuit
To provide an energy source

How should a voltmeter be connected in a circuit?

At the start of the circuit
In series with the component
In parallel with the component (correct)
In a closed loop

Which of the following statements about analogue voltmeters is true?

They can measure in microvolts
They are not subject to parallax error
They require reading from a specific angle to avoid errors (correct)
They are more accurate than digital voltmeters

What is a common problem associated with digital voltmeter displays?

They may flicker between values (A) Signup and view all the answers

What should be done before using a voltmeter?

Check for zero errors (B) Signup and view all the answers

What are the typical voltage ranges for analogue voltmeters?

0.1-1.0 V and 0-5.0 V (C) Signup and view all the answers

What happens when several cells are connected in series regarding their EMF?

The combined EMF is equal to the sum of their individual EMFs (B) Signup and view all the answers

What is a key advantage of digital voltmeters over analogue ones?

They provide more precise readings (D) Signup and view all the answers

What must be chosen before taking a measurement with either type of voltmeter?

The correct range (B) Signup and view all the answers

What is the definition of electromotive force (e.m.f.)?

It is the electrical work done by a source in moving a unit charge around a circuit (A) Signup and view all the answers

How is potential difference (p.d.) defined?

It is the work done by a unit charge passing through a component (D) Signup and view all the answers

What is the relationship between EMF and p.d. in a circuit?

E.m.f. and p.d. are different concepts with different measurements (D) Signup and view all the answers

When cells with the same EMF are connected in parallel, what is the resultant EMF?

It is equal to the EMF of any one of the cells (D) Signup and view all the answers

What is the unit of measurement for e.m.f and p.d.?

Volt (C) Signup and view all the answers

What is electromotive force (e.m.f.) primarily a measure of?

The electrical work done by a power source per unit charge (D) Signup and view all the answers

What is the unit of measurement for electromotive force?

Volts (D) Signup and view all the answers

If a charge of 1 coulomb has 2 joules of energy transferred to it, what is the potential difference?

2 volts (A) Signup and view all the answers

How is potential difference defined in a circuit?

The work done on a component per unit charge (B) Signup and view all the answers

What does a 12 V car battery represent in terms of electromotive force?

The potential difference of the power source in a circuit (D) Signup and view all the answers

What is the relationship between the potential difference and energy transferred in a circuit?

Potential difference depends on the amount of charge passing through a component (A) Signup and view all the answers

Which statement is true about the potential difference between two points in a circuit?

It is zero if no charge is moving (A) Signup and view all the answers

If a component in a circuit has a potential difference of 3V, how much energy is transferred per coulomb passing through it?

3 joules (C) Signup and view all the answers

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Study Notes

Electromotive Force (e.m.f.)

Electromotive force (e.m.f.), symbol E, represents the electrical work done by a source to move a unit charge around a complete circuit.
Formula: ( E = \frac{W}{Q} ), where ( W ) is work done and ( Q ) is charge.
Measured in volts (V).
Common examples include car batteries (12 V) and domestic mains supply (240 V).

Potential Difference (p.d.)

As charge flows in a circuit, energy is transferred from the power source to charge carriers and components, enabling devices like bulbs to light up.
Potential difference defines the work done by a unit charge as it passes through a component.
Formula: ( V = \frac{W}{Q} ).
1 volt is equivalent to transferring 1 joule of energy for each coulomb: ( 1 \text{ V} = 1 \text{ J/C} ).
If 2 joules are transferred per coulomb, the potential difference is 2 V.

Voltmeters

Used to measure potential differences across components and should be connected in parallel with the component.
Types:
- Digital voltmeters (precise and easier to read).
- Analogue voltmeters (subject to parallax error and require perpendicular reading).
Analog voltmeter ranges typically span from 0.1-1.0 V and 0-5.0 V; check for zero errors before use.
Digital voltmeters can measure small voltage differences (mV or µV) and might display fluctuating values requiring a judgement on reading.

Total Electromotive Force Calculations

In Series: Total e.m.f. is the sum of individual e.m.fs.
In Parallel: Resultant e.m.f. equals the e.m.f. of any one of the identical cells.

Key Definitions

e.m.f.: Work done by a source in moving a unit charge (represented by ( E = \frac{W}{Q} )).
p.d.: Work done on a component by a unit charge (represented by ( V = \frac{W}{Q} )).
Both e.m.f. and p.d. are measured in volts (1 V = 1 J/C).

Measurement and Calculation

Select an appropriate range on a voltmeter for accurate measurements; adjust if readings are off-scale.
Ensure both digital and analogue voltmeters are checked for zero errors before taking measurements.

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