Question
The current in a kettle is 10 A and the kettle is protected by a 13 A fuse.
The owner of the kettle replaces the 13 A fuse with a 3 A fuse.
What happens when the kettle is switched on?
The fuse melts and the kettle might be damaged.
The fuse melts and the kettle is undamaged.
The fuse does not melt and the kettle works correctly.
The fuse does not melt but the kettle fails to work.
Answer/Explanation
Ans: B
Question
A circuit-breaker is designed to protect a circuit which usually carries a current of 2 A.
The time taken to break the circuit depends on the current, as shown in the graph.
What happens when the current in the circuit is 2 A and what happens when the current is 18 A?
| when the current is 2 A | when the current is 18 A |
A | the circuit breaks in less than 0.01 s | the circuit breaks in less than 0.01 s |
B | the circuit breaks in less than 0.01 s | the circuit does not break |
C | the circuit does not break | the circuit breaks in less than 0.01 s |
D | the circuit does not break | the circuit does not break |
Answer/Explanation
Ans: C
Question
A domestic circuit includes a 30 A fuse. This protects the wiring if there is too much current in the circuit.
In which wire is the 30 A fuse positioned, and what does it do when it operates?
| position | operation |
A | live wire | disconnects the circuit |
B | live wire | reduces the current to 30 A |
C | neutral wire | disconnects the circuit |
D | neutral wire | reduces the current to 30 A |
Answer/Explanation
Ans: A