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Energy transfers
This topic links electricity to energy transfer over time, appliance power ratings, work done by charge flow and efficient power transmission.
34
Objectives
170
Flashcards
170
Questions
90 min
Study time
AQAGCSEPhysicsElectricity
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Syllabus checklist
What you need to know
34 objective pages available
Power10 objectives
- Explain that power transfer in a circuit device is related to potential difference across it and current through it.
- Explain that power transfer is related to energy changes over time.
- Recall and apply the equation P = V x I.
- Recall and apply the equation P = I^2 x R.
- Identify power P in watts, potential difference V in volts, current I in amperes and resistance R in ohms.
- Calculate electrical power from potential difference and current.
- Calculate electrical power from current and resistance.
- Rearrange power equations to calculate potential difference, current or resistance where appropriate.
- Apply MS 3b and MS 3c skills when calculating electrical power.
- Apply WS 4.5 when connecting circuit calculations to energy changes.
Energy transfers in everyday appliances15 objectives
- Describe everyday electrical appliances as devices designed to bring about energy transfers.
- Explain that energy transferred by an appliance depends on power and time switched on.
- Describe how domestic appliances transfer energy from batteries or ac mains to kinetic energy stores in motors.
- Describe how domestic appliances transfer energy from batteries or ac mains to thermal energy stores in heating devices.
- Explain that work is done when charge flows in a circuit.
- Recall and apply the equation E = P x t.
- Recall and apply the equation E = Q x V.
- Identify energy transferred E in joules, power P in watts and time t in seconds.
- Identify charge flow Q in coulombs and potential difference V in volts.
- Calculate energy transferred from power and time.
- Calculate energy transferred from charge flow and potential difference.
- Explain how the power of a circuit device relates to potential difference and current.
- Explain how the power of a circuit device relates to energy transferred over a given time.
- Describe relationships between appliance power ratings and changes in stored energy during use.
- Apply MS 3b and MS 3c skills when calculating electrical energy transfer.
The National Grid9 objectives
- Describe the National Grid as a system of cables and transformers linking power stations to consumers.
- State that electrical power is transferred from power stations to consumers using the National Grid.
- Explain that step-up transformers increase potential difference from power stations to transmission cables.
- Explain that step-down transformers decrease potential difference to a lower value for domestic use.
- Explain why a high potential difference in transmission cables reduces current for a given power transfer.
- Explain why reducing current in transmission cables reduces unwanted energy transfers.
- Explain why the National Grid is an efficient way to transfer electrical energy.
- Recognise that detailed transformer construction and operation is covered separately in Transformers (HT only).
- Apply WS 1.4 when explaining the efficiency of power transmission.
Key terms
powerpower transfer circuitpower transfer relatedrecallequationpower watts potentialelectrical power potentialelectrical power currentpower equations potentialskills calculating electricalapplyconnecting circuit calculations
Exam tips
- Power exam tip 1: Use precise subject-specific vocabulary when you explain how to explain that power transfer in a circuit device is related to potential difference across it and current through it..
- Power exam tip 1: Use precise subject-specific vocabulary when you explain how to explain that power transfer is related to energy changes over time..
Common mistakes
- Power common mistake 1: Answer by clearly explaining how to explain that power transfer in a circuit device is related to potential difference across it and current through it..
- Power common mistake 1: Answer by clearly explaining how to explain that power transfer is related to energy changes over time..
Practice preview
- Which option best matches the approved learning objective for Power (1)?
- A student is answering an AQA Electricity question about Power. Which choice best applies power transfer circuit?
- In Energy transfers, which revision statement keeps power transfer circuit tied to the approved learning objective?
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