Electricity

Worked examples (9)

• 1Match quantities to units (Getting started)
• 2What a current of 5 A means (Getting started)
• 3Define the volt (Getting started)
• 4What carries the current in a metal (Building confidence)
• 5Convert to base units (Building confidence)
• 6Where to connect the meters (Building confidence)
• 7Charge from current and time (Stretch)
• 8Why P = IV gives watts (Stretch)
• 9Is current used up? (Stretch)

Model answers (9)

• ✓Model answer — 4SD0/1P style
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Worked examples (9)

• 1State the difference (Getting started)
• 2Which supply does each device use? (Getting started)
• 3Mains voltage and frequency (Getting started)
• 4Identify a.c. and d.c. from traces (Building confidence)
• 5Find the frequency from a trace (Building confidence)
• 6What the trace below the zero line means (Building confidence)
• 7Why the mains uses a.c. (Stretch)
• 8Why a laptop needs an adapter (Stretch)
• 9Why a battery cannot supply a.c. (Stretch)

Model answers (9)

• ✓Model answer — 4SD0/1P style
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Worked examples (9)

• 1What a supply voltage means (Getting started)
• 2Direct E = QV substitution (Getting started)
• 3Rearrange to find the charge (Getting started)
• 4Find the charge first (Building confidence)
• 5Which voltage to use (Building confidence)
• 6Two routes to the same answer (Building confidence)
• 7Why series voltages add up (Stretch)
• 8Derive P = IV from E = QV (Stretch)
• 9Why mains is more dangerous than a battery (Stretch)

Model answers (9)

• ✓Model answer — 4SD0/1P style
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Worked examples (9)

• 1Why a resistor gets hot (Getting started)
• 2The three wires in a mains cable (Getting started)
• 3Insulation and double insulation (Getting started)
• 4The earthing and fuse sequence (Building confidence)
• 5Choose a fuse rating (Building confidence)
• 6Why the fuse goes in the live wire (Building confidence)
• 7Fuse against circuit breaker (Stretch)
• 8The consequences of the wrong fuse (Stretch)
• 9Explain the full safety system (Stretch)

Model answers (9)

• ✓Model answer — 4SD0/1P style
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Worked examples (9)

• 1Complete the meter readings (Getting started)
• 2Current at a junction (Getting started)
• 3Using V = I × R (Getting started)
• 4The two-resistor series calculation (Building confidence)
• 5Working backwards to a resistance (Building confidence)
• 6Three I-V characteristics compared (Building confidence)
• 7Investigate a characteristic (Stretch)
• 8LDRs and thermistors in use (Stretch)
• 9Why domestic lighting is parallel (Stretch)

Model answers (9)

• ✓Model answer — 4SD0/1P style
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Worked examples (9)

• 1Direct substitution (Getting started)
• 2What a power rating means (Getting started)
• 3Rearrange to find the current (Getting started)
• 4Convert kilowatts first (Building confidence)
• 5Choose a fuse (Building confidence)
• 6Comparing two appliances (Building confidence)
• 7Power then total energy (Stretch)
• 8Judging a fuse choice (Stretch)
• 9Why P = IV gives watts (Stretch)

Model answers (9)

• ✓Model answer — 4SD0/1P style
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• ✓Model answer — 4SD0/1P style

Worked examples (9)

• 1Charge from current and time (Getting started)
• 2Convert the time first (Getting started)
• 3Direct E = IVt substitution (Getting started)
• 4Two routes to the same energy (Building confidence)
• 5Rearrange for the time (Building confidence)
• 6Use the right voltage (Building confidence)
• 7Full multi-step chain (Stretch)
• 8Compare two appliances (Stretch)
• 9Work backwards to a voltage (Stretch)

Model answers (9)

• ✓Model answer — 4SD0/1P style
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• ✓Model answer — 4SD0/1P style