Electricity

What is a direct current

Where Electricity flows in one direction

What is the Uk mains electricity

Alternating current

What is a alternating current

Where current is constantly changing

What’s the benefit of a AC

Very easy to use a transformer to increase of decreasing PD

What’s the Uks AC frequency and P.D

Frequency of 50Hz

P.D of 230 V

What’s the difference bwteen AC and DC potential difference

In AC P.D constantly changes while in DC it remains constant

How to calculate frequency from graph

1/ seconds it take for wave to return back to original value

What is wires for electrical appliances made out of and why. What’s the costing mad out of

Copper as it’s a good conductor of electricity

Coating is made out of plastic which isn’t a good conductor

What colour is a live wire and what’s its function

Live wire is brown and carries Alternating potential difference from the Supply

What colour is the neutral wire and what’s its function

Blue and it’s job is to complete the circuit P.D is 0

What colour is the Earth wire and what it’s function

Green/Yellow striped and it’s the safety wire to stop appliance from becoming live

Why is the live wire dangerous and can be fatal

As live wire is 230V if someone touched it current would flow through person into the earth and they’d be electrocuted

Why is metal cases appliances dangerous

As if live wire is loose and touches case then case becomes live which could give someone a electrical shock

Why does the earth wire protect people from being electrical shocked if you touch metal case

As earth wire is connected into ground with a metal rod so if case becomes live a huge current flows to earth causing fuse to melt and shut off current preventing someone from getting an electrical shock when touching case.

What is the earth wire connected to

A fuse

What is an national grid

A system of transformers and high voltage cables

Why is energy always lost in the power cables

Due to resistance of the wires

Explain how electricity passes form appear stations to homes

1)Electricity passes through step up transformers which increases the potential difference to many volts

2)Eletricity then passes thought high voltage cables but cannot go into homes straight away has P.D is too high

3)So electricity passes through step-down transformer which reduces the potential difference to around 230V which is then passed into home

Why is step up transformers important

As less energy is lost in the power cables if they increase the potential difference to high amount

What is the resistance of a LDR in dark and light conditions

I’m dark Resistance is high while in light resistance is low

When temperature increase what happens to resistance in Thermistor

Resistance decrease

Why during cool conditions the P.D of a fan in a circuit is low

The Resistance of thermistor is high under cool conditions so it takes a lot of energy for current to pass so the P.D across thermistor is high so P.D across fan is low as P.D is shared in series circuits

How to calculate energy transferred involving power and time

Energy = Power(W) X Time(S)

What is the equation of power involving current and potential difference

Power = Current(C) X P.D(V)

How to calculate power involving current and

Power = (current)2 X Resistance

What does The Resistance tell us

Tell us the potential difference required to drive a current through a component

How to calculate resistance involving Current and Potential difference

Resistance = Potential difference/Current

Resistance will stay constant if….

Temperature is constant

Why is the current though a filament lamp not directly proportional to P.D

As the filament gets hot it causes resistance to increase. At high temps atoms in filament vibrate more so electrons in current collide more with atoms no more energy is needed to push current though filament.

Explain a current though a diode

Current in a diode flows in one direction as diode has high resistance in reverse direction

Explain LED

Gives off light when current flows through

The current is the same all around in which circuit

A series circuit

The P.D of shared all around in which circuit

A series circuit

How to calculate potential difference with current and resistance involved

P.D = Current X Resistance

The P.D is shared all around which circuit

A parallel circuit

A current is shared all around in which circuit

A parallel circuit