Course: Combined and Separate | Find each scene on YouTube, watch it, then answer the questions. Write your answers on paper first, then tap Show answer.
Equations you’ll need: Q = It · V = IR · P = VI · E = QV · E = Pt · T = 1 ÷ f
1. Frankenweenie – catching the lightning
🎬 The scene: In a thunderstorm, Victor raises Sparky on a platform with kites and metal rods to catch a lightning bolt.
Q1 (F) Victor uses metal rods and wires to catch the lightning. Why metal?
Show answer
Metals are good electrical conductors – charge flows through them easily.
Q2 (F/H) A lightning strike has a current of 20 000 A lasting 0.0005 s. Calculate the charge that flows.
Show answer
Q = It = 20 000 × 0.0005 = 10 C
Q3 (H) This charge moves through a potential difference of 100 000 000 V. Calculate the energy transferred.
Show answer
E = QV = 10 × 100 000 000 = 1 000 000 000 J (1 × 10⁹ J)
2. Ratatouille – struck by lightning on the roof
🎬 The scene: Remy and Emile hold a mushroom up on a metal TV aerial in a storm – and get struck by lightning.
Q1 (F) Why did the lightning strike the metal aerial the rats were standing on?
Show answer
It was the highest point and made of metal, a good conductor, so it gave the charge an easy path to the ground.
Q2 (F/H) Thunderclouds become charged by friction between ice particles. Explain how rubbing makes objects charged.
Show answer
Electrons (negative charge) are rubbed off one object onto the other. The object that gains electrons becomes negatively charged; the one that loses them becomes positively charged.
Q3 (H) A strike transfers 1 × 10⁹ J in 0.001 s. Calculate its power. Real or fake: could a rat survive this?
Show answer
P = E ÷ t = 1 × 10⁹ ÷ 0.001 = 1 × 10¹² W (a million million watts). Fake – a direct strike would almost certainly kill a small animal.
3. A Bug’s Life – “Don’t look at the light!”
🎬 The scene: Two mosquitoes outside the bug bar – one can’t resist flying into the glowing bug zapper.
Q1 (F) A bug zapper has two metal grids with a gap between them. Why does no current flow until an insect flies in?
Show answer
The air gap is an insulator, so the circuit is incomplete. The insect touches both grids and completes the circuit.
Q2 (F/H) The grids have a potential difference of 2000 V. An insect has a resistance of 100 000 Ω. Calculate the current through it.
Show answer
I = V ÷ R = 2000 ÷ 100 000 = 0.02 A
Q3 (H) Calculate the power transferred to the insect.
Show answer
P = VI = 2000 × 0.02 = 40 W – concentrated in a tiny insect, which heats it very quickly.
4. Despicable Me 2 – the lipstick taser
🎬 The scene: Agent Lucy Wilde zaps Gru with her lipstick taser and bundles him into her car.
Q1 (F) Why is the outside of a taser made of plastic?
Show answer
Plastic is an electrical insulator, so the person holding it doesn’t get a shock.
Q2 (F/H) Tasers use a very high potential difference. Use V = IR to explain why.
Show answer
Skin and clothing have a high resistance. A high potential difference is needed to push enough current through that resistance.
Q3 (H) Each pulse moves 0.0001 C of charge through 50 000 V. Calculate the energy in each pulse.
Show answer
E = QV = 0.0001 × 50 000 = 5 J
5. Toy Story 3 – resetting Buzz
🎬 The scene: The toys open Buzz’s back panel to reset him – and accidentally switch him into Spanish mode.
Q1 (F) Buzz is powered by two 1.5 V cells in series. What is the total potential difference?
Show answer
1.5 + 1.5 = 3 V. Cells in series add up.
Q2 (F/H) His voice circuit takes 0.2 A from the 3 V battery. Calculate its resistance.
Show answer
R = V ÷ I = 3 ÷ 0.2 = 15 Ω
Q3 (H) The toys flick a switch inside Buzz to change his mode. Draw a circuit with a battery, a switch and two components in parallel, so the switch only controls one of them.
Show answer
Draw the battery with two branches in parallel. Put a component on each branch, and put the switch on one branch only, in series with that component. The other branch stays on whether the switch is open or closed.
6. Monsters at Work – the blackout
🎬 The scene: The energy canisters run empty and Monsters, Inc. scrambles to stop a city-wide blackout.
Q1 (F) The city’s energy stores are running out and the lights start to fail. Why does a power station need to supply more electricity at some times of day than others?
Show answer
Demand changes – more people use electrical appliances at certain times (e.g. in the evening, when it’s dark or cold).
Q2 (F/H) A small city uses 50 000 000 W (50 MW). How much energy does it use in 1 hour?
Show answer
E = Pt = 50 000 000 × 3600 = 180 000 000 000 J (1.8 × 10¹¹ J)
Q3 (H) Suggest why real power stations keep some generators ready to switch on quickly.
Show answer
To meet sudden increases in demand or replace a generator that fails, so there is no blackout. Supply must always match demand.
7. Cloudy with a Chance of Meatballs – plugging into the sub-station
🎬 The scene: Flint’s house can’t power his food machine, so he runs a cable to the town’s power sub-station – with chaotic results.
Q1 (F) Flint’s house supply can’t power his machine. What is the potential difference of UK mains electricity?
Show answer
230 V (at a frequency of 50 Hz).
Q2 (F/H) A house supply can provide up to 100 A at 230 V. Calculate the maximum power.
Show answer
P = VI = 230 × 100 = 23 000 W
Q3 (H) His machine needs 1 000 000 W. What current would it draw at 230 V, and what would happen to the house wiring?
Show answer
I = P ÷ V = 1 000 000 ÷ 230 = 4300 A (to 2 s.f.). This huge current would make the wires overheat, so the fuse or circuit breaker would cut the supply to prevent a fire.
8. The Iron Giant – the power station
🎬 The scene: Hogarth finds the Giant eating the cables at a power sub-station and switches off the power to save him from electrocution.
Q1 (F) Why is it so dangerous to touch the wires at a sub-station?
Show answer
There is a very large potential difference between the wires and the ground, so a huge current would flow through your body to earth.
Q2 (F/H) The National Grid sends 1 000 000 W at 400 000 V. Calculate the current in the cables.
Show answer
I = P ÷ V = 1 000 000 ÷ 400 000 = 2.5 A
Q3 (H) Explain why the National Grid uses step-up transformers to transmit electricity at such a high potential difference.
Show answer
For the same power, a higher potential difference means a lower current. A lower current means less energy is wasted heating the cables, so transmission is more efficient. Step-down transformers then reduce the potential difference for safe use in homes.
9. The Boy Who Harnessed the Wind – building a wind turbine
🎬 The trailer: The true story of William Kamkwamba, who built a wind turbine from scrap and a bicycle dynamo to bring electricity to his village in Malawi.
Q1 (F) William uses a bicycle dynamo in his wind turbine. Describe the energy transfers from the wind to a light bulb.
Show answer
Kinetic energy of the wind → kinetic energy of the turbine blades → transferred electrically by the dynamo (generator) → light (and some heating) from the bulb.
Q2 (F/H) A 3 W bulb runs on 6 V. Calculate the current.
Show answer
I = P ÷ V = 3 ÷ 6 = 0.5 A
Q3 (H) How much energy does the bulb transfer in 4 hours? Give one advantage and one disadvantage of wind power for his village.
Show answer
t = 4 × 3600 = 14 400 s. E = Pt = 3 × 14 400 = 43 200 J. Advantage: renewable and free to run, with no fuel to buy. Disadvantage: unreliable – no electricity when there is no wind.
10. The Current War – Edison vs Westinghouse
🎬 The trailer: Thomas Edison (DC) and George Westinghouse (AC) race to light up America.
Q1 (F) Edison wanted direct current (DC). Westinghouse wanted alternating current (AC). What is the difference?
Show answer
DC flows in one direction only (e.g. from a battery). AC keeps changing direction (e.g. mains electricity).
Q2 (F/H) UK mains AC has a frequency of 50 Hz. Calculate its period.
Show answer
T = 1 ÷ f = 1 ÷ 50 = 0.02 s
Q3 (H) Westinghouse won. Explain why AC is used for the National Grid.
Show answer
Transformers only work with AC. They can step the potential difference up for transmission (reducing current and energy wasted heating cables) and down again for safe use in homes.
Teachers: the buttons open a YouTube search, so you can pick whichever upload is currently available. Please watch the clip through before showing it to a class.
