Starter quiz
- The number of coulombs that flow past a point each second equals the…
- charge.
- current. ✓
- electric field strength.
- force.
- velocity.
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- The unit of current is the…
- 'ampere' ✓
- A circuit which has only one loop is called a ______ circuit.
- 'series' ✓
- In a circuit, electrons flow through the wires away from the ______ end of the battery.
- 'negative' ✓
- In a circuit with a single loop, which of the following statements are correct?
- There is an electric field around the battery only.
- There is an electric field around the whole circuit. ✓
- Electrons nearest the battery experience the most force.
- Electrons experience the same force in all parts of the circuit. ✓
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- The equation relating current, charge and time is: current = charge ÷ time. Which of the following equations is the correct rearrngement of the equation with time as the subject?
- time = charge ÷ current ✓
- time = current ÷ charge
- time = current × charge
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Exit quiz
- Match the following quantities to its definition.
- resistance⇔a measure of how difficult it is for charge to move around a circuit ✓
- current⇔the amount of charge passing a point in one second ✓
- potential difference⇔a measure of the ‘push’ on electrons in a circuit ✓
- A series circuit contains only a cell and a lamp. Which of the following changes occurs if another lamp is added, in series with the first lamp?
- The current in the circuit decreases. ✓
- The potential difference of the cell decreases.
- The resistance of the circuit decreases.
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- In a series circuit, there is a particular type of relationship between current and total resistance: the current is ______ proportional to the total resistance, if the p.d. stays the same.
- 'inversely' ✓
- The potential difference across a 10 Ω resistor in a circuit is 4.0 V. What is the current in the resistor?
- 0.25 A
- 0.40 A ✓
- 2.5 A
- 40 A
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- A motor has a resistance of 6.0 Ω. What p.d. is needed to make a current of 1.5 A flow through the motor?
- 0.25 V
- 0.75 V
- 4.0 V
- 9.0 V ✓
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- A pupil has identical lamps and identical cells. He connects two cells and two lamps in series. Then he changes the circuit, but the current does not change. Which of the following could he have done?
- added one cell and added one lamp ✓
- removed one cell and removed one lamp ✓
- removed one lamp and added one cell
- removed one cell and added one lamp
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- The current in a series circuit is the same everywhere.
- The p.d. across each component in a series electric circuit adds up to the p.d. of the battery.
- The greater the resistance in a series circuit, the lower the current (current is inversely proportional to resistance).
- The greater the battery p.d. in series circuit, the larger the current (current is directly proportional to p.d.).
- Current, p.d. or resistance can be calculated with the equation: current = p.d./resistance.
Common misconception
Pupils often use physics equations without understanding, leading to errors.
Develop a qualitative understanding of potential difference, current and resistance before combining them mathematically. Use the equation as a shorthand for an already understood relationship between them.
Keywords
Series circuit - a circuit where there is only one loop
Potential difference (p.d.) - the voltage or a measure of the ‘push’ on electrons in a circuit
Resistance - a measure of how difficult it is for current to flow in a circuit
Electrical current - a measure of the amount of charge passing a given point in one second
Ohms (ω) - the unit of resistance
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