Starter quiz
- Which of the following is the unit of electric current?
- ampere ✓
- coulomb
- joule
- newton
- watt
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- Which of the following is the unit of resistance?
- coulomb
- joule
- ohm ✓
- volt
- watt
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- There is an invisible electric ______ around a charged object, in which other charged objects and small, uncharged objects experience forces.
- 'field' ✓
- Which of the following can always be used to describe a series circuit?
- 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.
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- 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.
- It decreases. ✓
- It stays the same.
- It is impossible to say without more information.
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- 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?
- The current multiplies by 3. ✓
- The current doubles.
- The current halves.
- The current divides by 3.
- The current stays the same.
-
Exit quiz
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?- 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.
- The readings are the same in A, B and C. ✓
-
In the circuit diagram, the resistances of the three components are shown. Which component has the highest p.d. across it?- component A ✓
- component B
- component C
- it is not possible to say without more information
-
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.- '0.9' ✓
- 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.
- '2.4' ✓
- What potential difference is needed to make a current of 0.40 A flow through a motor with resistance of 8.0 Ω?
- '3.2' ✓
- 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.
- '2.5' ✓
Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Current can be calculated using the equation: current = p.d. ÷ resistance (I = V ÷ R).
- The rules of current and p.d. for a series circuit can be applied to find some missing values of current and p.d.
- The equation I = V ÷ R can be rearranged so that either V or R is the subject of the equation.
- If any two values in the equation I = V ÷ R are known, the third can be calculated.
- 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.
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