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Year 10
OCR
Foundation

Analysing series circuits

I can use circuit rules and the equation I = V ÷ R to analyse series circuits.

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New
New
Year 10
OCR
Foundation

Analysing series circuits

I can use circuit rules and the equation I = V ÷ R to analyse series circuits.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. Current can be calculated using the equation: current = p.d. ÷ resistance (I = V ÷ R).
  2. The rules of current and p.d. for a series circuit can be applied to find some missing values of current and p.d.
  3. The equation I = V ÷ R can be rearranged so that either V or R is the subject of the equation.
  4. If any two values in the equation I = V ÷ R are known, the third can be calculated.
  5. If only one value in the equation I = V ÷ R is known, rules for current or p.d. need to be applied to find a 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.

Keywords

  • Electrical current - The amount of charge flowing past a given point in one second.

  • Series circuit - An electrical circuit with a single loop.

  • Potential difference (p.d.) - A measure of the push an electric field gives to charges.

  • Resistance - A property of a material that prevents the flow of current.

  • Ohms (Ω) - The unit of resistance.

A string loop or rope loop model is very useful for supporting discussion about rules in series circuits.
Teacher tip

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).

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Starter quiz

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6 Questions

Q1.
Which of the following is the unit of electric current?
Correct answer: ampere
coulomb
joule
newton
watt
Q2.
Which of the following is the unit of resistance?
coulomb
joule
Correct answer: ohm
volt
watt
Q3.
There is an invisible electric around a charged object, in which other charged objects and small, uncharged objects experience forces.
Correct Answer: field, feild
Q4.
Which of the following can always be used to describe a series circuit?
Correct answer: a circuit with only one loop
a circuit with only one component
a circuit with only one power source
a circuit in which every component has the same p.d.
Q5.
A lamp is added to a series circuit, in series with the other components in the circuit. No other changes are made to the circuit. Which of the following describes what happens to the current?
It increases.
Correct answer: It decreases.
It stays the same.
It is impossible to say without more information.
Q6.
A series circuit includes one 1.5 V cell. Two more 1.5 V cells are added in series with the first cell, and no other changes are made. Which of the following occurs?
Correct answer: The current multiplies by 3.
The current doubles.
The current halves.
The current divides by 3.
The current stays the same.

Exit quiz

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6 Questions

Q1.
The three circuit diagrams show the same cell in series with the same lamp. Which of the following statements about the voltmeter readings is correct?
An image in a quiz
The readings are all different in A, B and C.
The readings are the same in A and B but different in C.
The readings are the same in B and C but different in A.
Correct answer: The readings are the same in A, B and C.
Q2.
In the circuit diagram, the resistances of the three components are shown. Which component has the highest p.d. across it?
An image in a quiz
Correct answer: component A
component B
component C
it is not possible to say without more information
Q3.
The circuit diagram shows a series circuit. The potential difference across each cell and component is shown, except for the resistor. The p.d. across the resistor is V.
An image in a quiz
Correct Answer: 0.9, 0.9 V, 0.9V, 0.9 volts, 0.9volts
Q4.
While a lamp is switched on, its resistance is 50 Ω and the potential difference across it is 120 V. The current in the lamp is A.
Correct Answer: 2.4, 2.40, 2.4 A, 2.40 A, 2.4A
Q5.
What potential difference is needed to make a current of 0.40 A flow through a motor with resistance of 8.0 Ω?
Correct Answer: 3.2, 3.20, 3.2 V, 3.20 V, 3.2V
Q6.
A resistor in a circuit has a potential difference of 5.5 V across it and a current of 2.2 A flowing through it. The resistance of the resistor is Ω.
Correct Answer: 2.5, 2.50, 2.5 ohms, 2.50 ohms, 2.5 ohm