Electricity | OCR GCSE Combined Science Physics, Foundation tier (J250)
Electricity
- 161 questions
- 10 subtopics
- Paper 5 (Physics)
- Paper 5 (Physics)
Electricity is examined in Paper 5 (Physics).
It covers charge, and producing static electricity, transfer of electrons in charging and discharging, current as a rate of flow of charge, charge, current and time, series and parallel circuits, and circuit symbols, current, potential difference and resistance, resistors whose resistance changes, and investigating them, linear and non-linear circuit elements from graphs, net resistance in series and parallel and circuits for measurement, and electrical power.
Sample questions from Electricity
Answer each one closed book first, then open the answer.
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Charge, and producing static electricity
An object has more electrons than protons. What is the sign of its overall charge?
Show the answer
Negative, because the negative charge is no longer balanced by the positive charge. -
Transfer of electrons in charging and discharging
A polythene rod is rubbed with a cloth and becomes negatively charged. Explain what has happened.
Show the answer
Electrons have been transferred from the cloth onto the rod, giving the rod more electrons than protons. -
Current as a rate of flow of charge
A closed loop of copper wire on its own carries no current. Which condition is missing?
Show the answer
There is no source of potential difference to push the charge round. -
Charge, current and time
A charge of 90 C passes a point in 30 s. What is the current?
Show the answer
3 A, because 90 C ÷ 30 s = 3 A. -
Series and parallel circuits, and circuit symbols
A cell supplies two branches, one carrying 0.4 A and the other 0.6 A. What current comes out of the cell?
Show the answer
1.0 A, because the branch currents add up to the current from the cell. -
Current, potential difference and resistance
What is meant by the resistance of a component?
Show the answer
How strongly it opposes the flow of charge through it. -
Resistors whose resistance changes, and investigating them
How does the resistance of a thermistor change as it gets hotter?
Show the answer
Its resistance falls as its temperature rises. -
Linear and non-linear circuit elements from graphs
Why should a current against potential difference graph for a resistor pass through the origin?
Show the answer
With no potential difference across it there is nothing to push charge through it, so the current is zero.
The 10 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Charge, and producing static electricity | Positive and negative charge in all matter, zero net charge and the sign of an object that gains or loses electrons, the coulomb, producing static by rubbing, attraction and repulsion without contact, why insulators hold charge, and sparks, car-door shocks and earthing a fuel tanker. | 16 |
| Transfer of electrons in charging and discharging | Which particles move when insulators are rubbed and why protons stay put, how polythene and acetate rods charge oppositely, why the charges on the rod and the cloth are equal and opposite, why rubbing works where resting does not, and how a charged sphere discharges through a person to earth. | 8 |
| Current as a rate of flow of charge | Current as the rate of flow of charge, the electrons that carry it in a metal, the two conditions for charge to flow, the ampere and the ammeter, conventional current, and why the current is the same at every point in a single loop and is not used up in a lamp. | 16 |
| Charge, current and time | The relationship between charge, current and time, the units of each, worked examples finding charge, current or time, and how charge compares for two components carrying different currents. | 9 |
| Series and parallel circuits, and circuit symbols | How charge travels in series and parallel circuits, connecting ammeters and voltmeters, how potential difference and current are shared between components and branches, and the symbols for cells, batteries, fixed and variable resistors, lamps, diodes, light dependent resistors, thermistors, meters and switches. | 18 |
| Current, potential difference and resistance | Potential difference as energy transferred per coulomb, the volt, the ohm and what resistance means, how current responds to changes in potential difference and resistance, and calculations with potential difference = current × resistance, including why current is proportional to potential difference when resistance is constant. | 16 |
| Resistors whose resistance changes, and investigating them | What constant resistance means, why a filament lamp and a heated wire resist more, how diodes, thermistors and light dependent resistors behave, and circuits for investigating each of them. | 16 |
| Linear and non-linear circuit elements from graphs | Straight and curved graphs of current against potential difference, finding resistance from readings and from a graph, the characteristic graphs of a fixed resistor, a filament lamp and a diode, resistance graphs for a thermistor and a light dependent resistor, and plotting results with y = mx + c and a line of best fit. | 19 |
| Net resistance in series and parallel | How adding a resistor in the same loop or on a new branch changes net resistance, what that does to lamp brightness and current, and calculations of net resistance and potential difference. | 16 |
| Circuits for measurement, and electrical power | A circuit for testing whether resistance is constant, why ammeters need low and voltmeters high resistance, thermistor and diode test circuits, and calculations linking power, potential difference, current and energy. | 27 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR GCSE Combined Science Physics, Foundation tier Active Recall Guide
Every topic, not just this one. 1,084 questions with their answers.