Pedalling an exercise bike spins a magnet within a coil, so a potential difference is induced in a circuit. Figure 10 plots that potential difference against time during a ride.
Choose what the coil must connect to so the circuit carries direct current.
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A split ring commutator. It swaps the connections to the coil every half turn, so the current in the circuit always goes the same way round. Slip rings keep the connections steady, so the output stays alternating. An ammeter only measures current, and a switch only turns it on or off.
How the marks are earned
- Tick the commutator made from a split ring.
- One box only: two ticks earn nothing.
Use Figure 10 to choose the feature showing that direct current is produced.
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A potential difference that never goes below the time axis always pushes current the same way round, which is direct current. Alternating current would swing below the axis, giving negative values. A repeating peak, a drop to zero, and a change over time all happen with alternating current too, so they cannot show direct current.
How the marks are earned
- Tick the option saying the potential difference never goes negative.
- One box only: two ticks earn nothing.
State what makes an energy resource renewable.
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A renewable resource can be replaced or regrown as fast as it is used, so it is not finite and does not run out.
How the marks are earned
- Any one of: it can be replenished; it can be regrown; it will not run out. Saying it is not finite is accepted. Naming examples such as solar, saying it can be renewed or got back, saying it won't get used up or avoids finite resources, and mentioning emissions all earn nothing.
Decide if the rider-powered electricity counts as renewable or not, and justify your choice.
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Renewable: the power comes from the rider, who gets energy from food that can be regrown and replaced.
How the marks are earned
- Either choice earns the mark if the reason fits. Renewable: the rider gets energy from food that can be grown again. Non-renewable: the rider's supply of energy is limited, and once tired they stop producing electricity.
Why it scores
The other route also earns the mark. A student can argue that it is non-renewable, because the rider's energy is limited and they cannot generate any more once they are tired. What matters is that the reason matches the choice.
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