Mains Electricity Flashcards
What is AC current?
Alternating Current- current which changes direction constantly
What is DC current?
Direct current- Current which flows in only one direction through a circuit
How does the oscilloscope change when the current increases with AC current?
the amplitude increases
How does the oscilloscope change when the frequency increases with AC current?
The frequency of the wave increases
What does DC current look like on an oscilloscope?
A straight horizontal line
What type of current is mains electricity?
AC
What type of current is a battery?
DC
What are the colours and names of the 3 wires in a 3 pin plug?
Live (brown), Earth (yellow and green stripes), Neutral (blue)
What is the potential difference of mains electricity?
230V
When looking at a plug from above, what is the order of the 3 wires from left to right?
Neutral, Earth, Live
What is the job of the live wire?
It carries alternating current from the mains
What is the job of the neutral wire?
It completes the circuit
What is the job of the earth wire?
It connects to the metal casing of an appliance and the ground, so that if the live wire becomes loose and touches the casing, the appliance won’t become live and can’t shock people.
Why should you never touch the live wire, even when the appliance is turned off?
You could touch the wire before the switch, where current still flows.
Why should you never touch the neutral wire?
The appliance could have been wired the wrong way around, making the neutral wire into the live wire.
What is a fuse?
A thin wire which melts if too much current flows through it, breaking the circuit.
What are the potential differences of the three wires?
Live - 230 V
Neutral - at or close to 0 V
Earth - 0 V
What is power?
The rate of transfer of energy
What is the equation connecting power, time and energy?
P = E / t power = energy / time
What is the equation connecting potential difference, power and current?
P = I V power = current x potential difference
What is the equation connecting charge, energy and potential difference?
E = Q V energy = charge x potential difference
What is the unit of measurement for power?
Watts (W)
What is the equation connecting power, resistance and current?
P = I^2 R power = current^2 x resistance
what are the equations for efficiency?
efficiency = useful power out / total power in efficiency = useful energy out / total energy in
