S2 LSS Chapter 13C Effects, Hazards and Safety Features in the Electric Circuit
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Label the wires in a three-pin plug. (Flip flashcard for diagram)
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Explain chemical effect. Give an example of the effect.
- A chemical change takes place when an electric current passes through chemical solutions Example: electrolysis, extraction of metals, electroplating an object (coating object with thin layer of metal)
What is the function of a circuit breaker?
- A circuit breaker breaks the circuit when the current exceeds the circuit breaker's rating. - It isolates the equipment from the mains to protect the equipment and the cable from overheating.
Explain magnetic effect. Give an example of the effect.
- A temporary magnet is made when electric current passes through a coil of wire. - It is easily turned on and off by a switch Example: motor, magnetic resonance imaging
Explain heating effect. Give an example of the effect.
- Electrical energy converted to thermal energy when passed through a heating element made of a high resistance material that can withstand high temperature Examples: electric kettle, electric iron, infant incubator
What is the function of the earth wire?
- When the live wire touches the metal casing in a fault, the earth wire provides a path of lower resistance for the current to flow through, thus preventing electrocution. - The large current drawn will blow the fuse/circuit breaker and break the circuit.
State three hazards of electricity.
1. Damaged insulation 2. Overloading of cables 3. Wet/damp conditions 4. Tampering of power sockets
State two physical properties of a heating element
1. High melting point 2. Low electrical resistance
State two ways how the strength of an electromagnet can be increased.
1. Increasing the current 2. Inserting an iron core into the coil of wire
Describe four ways to prevent electrocution when using electrical appliances.
1. Never use electrical appliances in wet places 2. Get replacement or repair when electric wiring is old and insulation is peeling off, exposing the wires 3. Switch off and pull out the plug from the socket before cleaning electrical appliances 4. Never insert any item into an electrical socket.
Explain how overloading of cables can cause a fire
A large current is drawn from the power supply, which releases a large amount of heat/excessive heat.
A plug is connected to a heater with a current rating of 5A, and a voltage of 240V. Write down the current and voltage across the live, neutral and earth wires.
Live wire: 5A, 240V Neutral wire: 5A, 0V Earth wire: 0A, 0V
State the colour of the wires in the three-pin plug.
Live wire: Brown Neutral wire: Blue Earth wire: Green and yellow
Which wire is the fuse, switch and circuit breaker connected to? Why?
The fuse, switch and circuit breaker is connected to the live wire, which helps to complete isolate the mains from the appliance.
State the functions of the live wire and neutral wire.
The live wire carries the current from the mains to the appliance. The neutral wire carries the current from the appliance to the mains.
What is the function of a fuse?
To break the circuit when the current exceeds the fuse rating.
Explain how water can increase risk of electrocution/electric shocks.
Water reduces skin resistance, thus allowing for electricity to be conducted, and an electric current to pass through.
State the three effects of an electric current.
heating effect, magnetic effect, chemical effect