Safe Electricals Flashcards
Describe and recognise how resistors can be used to change the current in a circuit
A variable resistor (rehostat) has a resistance that can be altered. A current that flows can be changed by simply moving the sliding contact if the variable resistor from one end to another
Describe how variable resistors can be used to change the current in a circuit
- longer wires give less current
- thinner wires give less current
What is resistance measure in
Ohms
Recall the colour coding for live, neutral and earth wires
Live - brown
Neutral - blue
Earth - green/yellow
State that an earthed conductor cannot become live
This is because earthing means connecting the conductor to earth, which takes away any charge that could electrocute people
Describe reasons for the use of fuses and circuit breakers
They are safety features; prevent fires, injury and death in the home by breaking the circuit of an appliance if a fault occurs
A circuit breaker can be reset. A fuse has to be replaced.
Recognise that double insulated appliances don’t need earthing
The appliance is a non conductor and cannot become live
Explain how variable resistors can be used to change the current in a circuit
Longer wires have more resistance
Thinner wires have more resistance
Describe the relationships between current, voltage and resistance:
- for a given resistor, current increases as voltage increases and vice versa
- for a fixed voltage, current decrease as resistance increases and vice versa
Equation for resistance
Resistance = voltage / current
Describe the functions of the live, neutral and earth wires
Live - carries the high voltage
Neutral - completes the circuit
Earth - a safety wire to stop the appliance becoming live
Calculate power
Power = voltage X current
Explain how a wire fuse reduces the risk of fire; if the appliance develops a fault:
- too large a current causes the fuse to melt
- preventing flow of current
- prevents flex overheating and causing fire
- prevents further damage to appliance
Explain the behaviour of simple circuits in terms of the flow of electric charge
A circuit is a complete loop that allows an electric current to flow. Electrons flow around the circuit from the negative electrode of the power source to the positive electrode.
