This solar-powered security light is fitted outside a house. Fig. 1 shows its rechargeable battery, LED lamp and light sensor. In daylight, the solar panel ...
Question 1 Report
This solar-powered security light is fitted outside a house. Fig. 1 shows its rechargeable battery, LED lamp and light sensor. In daylight, the solar panel transfers energy to the battery. When the light level falls, the sensor switches on the LED circuit. The owner wants the light to operate automatically at night while using as little stored energy as possible. The LED has a lower power rating than an old halogen security lamp.
(a) What is the useful energy store increased by the solar panel in daylight? [1]
(b) When does the light sensor switch on the LED? [1]
(c) Describe two reasons why an LED is suitable for this security light. [3]
At a holiday cottage, a consumer unit contains circuit breakers instead of replaceable fuses. Fig. 1 shows one circuit breaker supplying sockets in a bedroom. A damaged cable in a bedside lamp causes the live and neutral wires to touch. The current rises quickly above the value marked on the circuit breaker. The owner resets the breaker only after the lamp has been removed and checked. This avoids repeatedly restoring a fault in the circuit.
(a) What happens to the current when the two wires touch? [1]
(b) Describe how the circuit breaker protects the cable. [2]
(c) Give one advantage of a circuit breaker compared with a fuse. [2]
Answer Details
Solar security light
- (a) In daylight, the solar panel increases the chemical energy store of the battery. [1]
- (b) The sensor switches on the LED when light intensity falls, meaning when it becomes dark. [1]
- (c) An LED has low power, so it transfers less stored energy each night. It still gives useful light, and it lasts longer than a filament or halogen lamp. These are three valid reasons for using it in an automatic security light. [3]
Circuit breaker
- (a) When the live and neutral wires touch, the current becomes very large, or increases sharply. This is a short circuit. [1]
- (b) The breaker detects the excess current and opens the circuit. Opening the circuit stops the current, preventing the cable becoming dangerously hot. [2]
- (c) A circuit breaker can be reset after the fault has been removed and does not need replacing. It can also operate faster than a fuse. Any two valid advantages gain credit. [2]
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