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Year 10
OCR
Foundation

Adding components to a parallel circuit

I can use the rules for current and potential difference in a parallel circuit and explain the effects of adding a component.

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New
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Year 10
OCR
Foundation

Adding components to a parallel circuit

I can use the rules for current and potential difference in a parallel circuit and explain the effects of adding a component.

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Lesson details

Key learning points

  1. The p.d. across each branch of a parallel circuit is the same as the p.d. across the battery.
  2. The current through each branch of a parallel circuit adds up to the current through the battery.
  3. Adding a component in a new branch of a parallel circuit reduces the resistance of the circuit.
  4. Adding a component to an existing branch of a parallel circuit increases the resistance of the circuit.
  5. The p.d. across the terminals of a battery does not change when components are added to a circuit.

Keywords

  • Electric charge - an electrical property; it can either be positive or negative

  • Parallel circuit - a circuit with separate branches connected to the battery

  • Electric field - the invisible field around a charged object that causes other charges to experience a force

  • Potential difference (p.d.) - the voltage or a measure of the ‘push’ on electrons in a circuit

  • Electric current - a measure of the amount of charge passing a given point in one second

Common misconception

To solve circuits you need only to put numbers into equations.

Talk through circuits with pupils before analysing them in order to develop an intrinsic understanding of how circuits work; research shows this improves pupils’ problem solving ability for electric circuits.

Demonstrate the key learning points so that they can be emphasised. Online simulators will be useful in showing how values change in a clear manner.
Teacher tip

Equipment

1.5 V cells, identical bulbs in holders, ammeters and electrical leads

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Electric current at a point in a circuit is the amount of charge passing that point…
per coulomb.
per joule.
Correct answer: per second.
per volt.
Q2.
P.d. is a shorter way of writing the electrical quantity .
Correct Answer: potential difference, the potential difference
Q3.
Which of the following statements about batteries are correct?
Correct answer: There is an electric field around a battery.
Correct answer: The ends of a battery have opposite electric charges.
Two or more batteries connected in series are called a cell.
Q4.
Which of the following statements is correct?
A cell has a fixed current but not a fixed p.d.
Correct answer: A cell has a fixed p.d. but not a fixed current.
A cell has both a fixed current and a fixed p.d.
A cell has neither a fixed current nor a fixed p.d.
Q5.
A cell and a lamp are connected in series. A second, identical lamp is then connected in series with the first lamp. Which of the following statements describes what happens to the first lamp?
It gets brighter.
Correct answer: It gets dimmer.
Its brightness stays the same.
Q6.
A series circuit contains a battery and three different resistors. Which of the following statements about the circuit are correct?
Correct answer: The current is the same in every resistor.
The current is different in each resistor.
The p.d. is the same across every resistor.
Correct answer: The p.d. is different across each resistor.

Exit quiz

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6 Questions

Q1.
The circuit diagram shows a circuit with parallel branches. The branches have different resistances. Which of the following statements is correct?
An image in a quiz
Correct answer: The p.d. is the same across each branch.
The p.d. is higher across branches with lower resistance.
The p.d. is higher across branches with higher resistance.
The sum of p.d.s across all the components equals the p.d. across the battery.
Q2.
The circuit diagram shows a circuit with parallel branches. The branches have different resistances. Which of the following statements is correct?
An image in a quiz
The current is the same in each branch of the circuit.
Correct answer: The current in the battery equals the sum of the currents in the branches.
The current in the battery equals the average of the currents in the branches.
Q3.
A parallel circuit has two branches. A resistor is added to one of the branches. Which of the following statements is correct?
The current in that branch increases.
The current in the battery increases.
Correct answer: The resistance of the whole circuit increases.
The potential difference across the branch increases.
Q4.
A new branch, containing components, is added to a parallel circuit. Which of the following statements are correct?
Correct answer: The current in the battery increases.
The current in the battery decreases.
The resistance of the circuit increases.
Correct answer: The resistance of the circuit decreases.
Q5.
A series circuit contains a battery and one lamp. A second, identical lamp is added, in parallel with the first lamp. Which of the following statements is correct?
The first lamp becomes dimmer.
The first lamp becomes brighter.
Correct answer: The brightness of the first lamp does not change.
Q6.
A series circuit contains a battery and one lamp. A second, identical lamp is added, in parallel with the first lamp. Which of the following statements is correct?
The battery lasts longer.
Correct answer: The battery does not last as long.
The battery lasts for the same length of time.

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