These are some of the necessary electrical symbols that you must know. Those in grey background are for Pure Physics.
How wonderful it is if Singapore can be powered by the sun.
Lighting circuit, in fact all circuits at home, should be connected in parallel.
When one bulb is spoilt or switched off, the rest of the bulbs can still function normally at normal brightness. This is because the potential difference across each bulb in the branches remains the same.
If the lighting circuit is connected in series, when one bulb is spoilt or switched off, it will be an open circuit and no current can flow through the circuit. Hence all the bulbs cannot function.
A fuse is a safety device that is added to an electrical circuit to prevent excessive current flow. It has the same function as a circuit breaker. However , a fuse must be replaced once it melts (blows). A circuit breaker can be reset after it trips.
Electric symbol for fuse
Fuse is connected to the live wire. It consists of a short piece of thin wire. In the event of an electrical fault, when a current that exceeds its fuse rating flows through, it heats up and melts (fuse blows). When the fuse blows, the electrical appliance is disconnected from the high potential of the live wire (usually 240 V). Hence it protects the appliance and the user.
The choice of fuse is always slightly higher than the actual current flowing through the appliance, and it has to be a whole number. Typical household fuses off the shelves are rated at 1 A, 2 A, 3 A, 5 A, 10 A and 13 A. But in theory, we just state a fuse which is slightly higher and is a whole number.
An electric cable contains three wires live, neutral and earth. The cable is correctly wired to a plug which contains a 3A fuse. The insulation becomes damaged and bare metal wires show.
Five possible events can occur.
How many of these five events cause the fuse in the plug to blow?
A 1 B 2 C 3 D 4
Solutions: Option B
Consider the five events: