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Questions and Answers
What is the main function of a voltmeter?
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?
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?
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?
What is a common problem associated with digital voltmeter displays?
What should be done before using a voltmeter?
What should be done before using a voltmeter?
What are the typical voltage ranges for analogue voltmeters?
What are the typical voltage ranges for analogue voltmeters?
What happens when several cells are connected in series regarding their EMF?
What happens when several cells are connected in series regarding their EMF?
What is a key advantage of digital voltmeters over analogue ones?
What is a key advantage of digital voltmeters over analogue ones?
What must be chosen before taking a measurement with either type of voltmeter?
What must be chosen before taking a measurement with either type of voltmeter?
What is the definition of electromotive force (e.m.f.)?
What is the definition of electromotive force (e.m.f.)?
How is potential difference (p.d.) defined?
How is potential difference (p.d.) defined?
What is the relationship between EMF and p.d. in a circuit?
What is the relationship between EMF and p.d. in a circuit?
When cells with the same EMF are connected in parallel, what is the resultant EMF?
When cells with the same EMF are connected in parallel, what is the resultant EMF?
What is the unit of measurement for e.m.f and p.d.?
What is the unit of measurement for e.m.f and p.d.?
What is electromotive force (e.m.f.) primarily a measure of?
What is electromotive force (e.m.f.) primarily a measure of?
What is the unit of measurement for electromotive force?
What is the unit of measurement for electromotive force?
If a charge of 1 coulomb has 2 joules of energy transferred to it, what is the potential difference?
If a charge of 1 coulomb has 2 joules of energy transferred to it, what is the potential difference?
How is potential difference defined in a circuit?
How is potential difference defined in a circuit?
What does a 12 V car battery represent in terms of electromotive force?
What does a 12 V car battery represent in terms of electromotive force?
What is the relationship between the potential difference and energy transferred in a circuit?
What is the relationship between the potential difference and energy transferred in a circuit?
Which statement is true about the potential difference between two points in a circuit?
Which statement is true about the potential difference between two points in a circuit?
If a component in a circuit has a potential difference of 3V, how much energy is transferred per coulomb passing through it?
If a component in a circuit has a potential difference of 3V, how much energy is transferred per coulomb passing through it?
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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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