Copy each passage into your book and fill in the numbered gaps using the word bank. Then check your answers. ← All topics
1. Current and charge (C+S)
Electric current is the rate of flow of electrical (1)______. Current is measured in (2)______ (A) and charge in (3)______ (C), and they are linked by Q = It. For a current to flow there must be a (4)______ circuit and a source of potential difference. In a single closed loop, the current is the (5)______ at every point.
Word bank: amperes · charge · closed · coulombs · same
Check your answers
1 charge · 2 amperes · 3 coulombs · 4 closed · 5 same
2. Potential difference and resistance (C+S)
Potential difference is measured with a (1)______ connected in (2)______ with the component. Current is measured with an (3)______ connected in (4)______. The equation linking them is V = IR. For a fixed potential difference, the greater the resistance, the (5)______ the current.
Word bank: ammeter · parallel · series · smaller · voltmeter
Check your answers
1 voltmeter · 2 parallel · 3 ammeter · 4 series · 5 smaller
3. Components and I–V graphs (C+S)
In an (1)______ conductor at constant temperature, the current is directly proportional to the potential difference, so the resistance stays the same. In a filament lamp, as the current increases the filament gets hotter and its resistance (2)______. A (3)______ only lets current flow in one direction. The resistance of a thermistor decreases as (4)______ increases, and the resistance of an LDR decreases as (5)______ intensity increases.
Word bank: diode · increases · light · ohmic · temperature
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1 ohmic · 2 increases · 3 diode · 4 temperature · 5 light
4. Series and parallel circuits (C+S)
In a series circuit, the (1)______ is the same through each component, the total potential difference is (2)______ between the components, and the total resistance is the (3)______ of the individual resistances. In a parallel circuit, the (4)______ across each branch is the same, and the total current is the sum of the currents in the branches. Adding a resistor in parallel makes the total resistance (5)______.
Word bank: current · potential difference · shared · smaller · sum
Check your answers
1 current · 2 shared · 3 sum · 4 potential difference · 5 smaller
5. Mains electricity (C+S)
UK mains electricity is an (1)______ current supply with a frequency of (2)______ Hz and a potential difference of about 230 V. Cells and batteries supply (3)______ current. In a three-core cable, the live wire is brown, the neutral wire is (4)______ and the earth wire is green and yellow. The earth wire is a (5)______ wire that stops the appliance becoming live. The live wire can still be dangerous when the switch is (6)______.
Word bank: 50 · alternating · blue · direct · off · safety
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1 alternating · 2 50 · 3 direct · 4 blue · 5 safety · 6 off
6. Power and energy transfers (C+S)
The power of a circuit device can be found using P = VI or P = I²R – remember to (1)______ the current. The energy transferred depends on the power and how long the appliance is used for: E = P(2)______. Energy is also transferred when charge flows through a potential difference: E = Q(3)______. The power rating of an appliance tells you the energy it transfers every (4)______.
Word bank: second · square · t · V
Check your answers
1 square · 2 t · 3 V · 4 second
7. The National Grid (C+S)
The National Grid is a system of cables and (1)______ linking power stations to consumers. (2)______ transformers increase the potential difference, which (3)______ the current in the transmission cables. A smaller current means less energy is lost (4)______ the cables, so transmission is more (5)______. Step-down transformers then reduce the potential difference to a (6)______ level for homes.
Word bank: decreases · efficient · heating · safer · step-up · transformers
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1 transformers · 2 step-up · 3 decreases · 4 heating · 5 efficient · 6 safer
8. Static electricity (S only)
When two insulating materials are rubbed together, (1)______ are transferred from one to the other. The material that gains them becomes (2)______ charged, and the other becomes positively charged. Like charges (3)______ and unlike charges attract. A charged object creates an electric (4)______ around itself, which is strongest (5)______ to the object. If the field is strong enough, a spark can jump across a gap.
Word bank: closest · electrons · field · negatively · repel
Check your answers
1 electrons · 2 negatively · 3 repel · 4 field · 5 closest
