P2.5 Mains electricity

hot room lighting low voltage

Bulbs- Low energy bulbs are more efficient because they don't become ___. Types of these include - low energy compact fluorescent bulbs which are used for ____ ____. - LEDS that operate at ___ ___/power, they're more efficient and last longer.

filament bulbs plastic parts brittle

Bulbs- ____ ____ are inefficient because the energy from the bulb gradually makes the _____ ____ of the bulb socket _____.

copper wires thickness larger currents heating effect

Cables- consists of 2/3 insulated ___ ____. Cables of different ______ are used for different purposes, thicker cables are used for ____ ____ as thicker wires will be needed to reduce the ____ ____ of the current.

copper good conductor plastic insulator

Cables- the mains electricity cable controls 2/3 inner wires, each with a core of _____ as this is a ____ _____. The outer layers of the wire are flexible _______ which is a good electrical _____.

work faster

Circuit breakers- are used instead of fuses because they ____ ____ and can be reset more quickly.

electromagnetic switch in series magnetic field

Circuit breakers- circuit breakers act as resettable fuses. - it is an ________ _____, which opens when there is a fault to stop the current in the live wire flowing. - the electromagnet is ___ ____ with the live wire, so if the live wires current is too large, the ____ ____ is strong enough to pull the switch contacts apart.

constantly changes direction 230v 50

Current - Alternating current ____ ____ ____. Mains electricity is an AC supply at ______ with a frequency of ____Hz

direct current batteries

Current- ____ ____ flows in one directly only, _____ and cells supply this current.

neutral wire large positive value

Current- every mains circuit has a live wire and a ____ ____. The potential difference of the live terminal varies between a ____ ___ ____ and a negative one, which makes it dangerous.

0

Current- in a mains circuit, the neutral terminal has a potential difference of ____.

metal cases touches

Earthing- many electrical appliances have ____ ____. The earth wire thus creates a safe route for the current to flow through if the live wire _____ the casing.

plastic casings double insulation

Earthing- some appliances do not have an earth wire because they have ____ ____ which gives the appliance ____ _____.

metal casing

Earthing- the earth terminal is connected to the _____ _____, so that the current will flow through it as oppose to the metal casing.

low resistance potential difference

Earthing- the earth wire has a ____ ____,so a strong current will surge through it in order to maintain the same ____ ____. This high current melts the fuse.

plugs switched off

Electrical issues Electrical faults occur is sockets, _____or appliances are damaged. - if the fuse blow or the circuit breaker trips, the appliance must be ____ _____.

overheats disconnected

Electrical issues - if the appliance _________, switch it off. - too many appliances connected to a socket may cause this to happen os the appliances should be _____.

thin wire current

Fuses- a fuse contains a ____ ____ that heats up and melts if too much current passes through, which cuts of the _____.

3A higher current

Fuses- fuses in plugs are made in standard ratings, the most common being _____, 5A, and 13A. The fuse should be rated at a slightly ___ ____ than the device needs.

oscilloscopes frequency

Measuring AC- ______ are used to measure peak potential difference and _____ of a low voltage ac supply.

maximum vertical deviation y gain control

Measuring AC- on an oscilloscope - to measure peak voltage, the ____ ___ ____ of the trace from the centre line is measure from the screen. - the number of divisions multiplied by ___ ____ ____ from the controls.

plastic touch eachother

Plugs- the case is made of _____ as this is an insulator. The inside of the case is shaped so the wires and pins cant ____ ____.

energy transferred (j) / time (seconds)

Power (watts) =

faster different neutral sensitive

Residual current circuit breakers work even ___. - it cuts of the current in the live wire when it is _____ from the current in the _____. - it is more _____ than a fuse or ordinary CB

brown wire high voltage

The ______ _____ is the live wire, and this carries a ____ _____.

neutral wire completes circuit

The blue wire is the ____ ____. This ______ the _____.

yellow safety wire

The green and _____ wire is the earth wire. This is a _____ ____ to stop the appliance from becoming live.

electrical energy power

Using electrical appliances transfers ____ ____ into other forms of energy. The ______ of the appliance is the energy it transfers.

vibrating metal ions kinetic energy hot

When a resistor is connected to a battery, electrons pass through the resistor, colliding with ____ ___ ___ of the resistor which transfer energy to them. They gain ____ ____, which causes them to vibrate more and thus the resistor gets ____.

current (a) x time (seconds)

charge (coulombs) =

potential difference (v) x charge (c)

energy transferred (j) =

1/ time for one cycle

frequency of an ac supply =

time taken for one oscillation

period of ac =

current (a) x potential difference (v)

power supplied (watts) =