Engineering - electrical systems

what is a mains power supply

A constant source of electricity of 230V supplied by a 3 prong plug

4 advantages of a Mains power supply

-relatively cheap

-available constantly

-high voltage + current

-available in most homes

3 appliances that typically use Mains power

-toaster

-hair straighteners

-kettle

alternating current graph

3 prongs on a plug

live, earth and neutral

What is a battery power supply?

2 terminals (anode + cathode) and an electrolyte. It uses a chemical reaction which is converted to electrical energy.

What is the potential difference of a cell?

1.5V

What is the difference between a battery and a cell?

A battery is a collection of cells, a cell is singular

4 benefits of rechargeable batteries

-not thrown away as often

-better for the environment

-cheaper long term

-can be reused

2 disadvantages of rechargeable batteries

-1.2 volts<1.5 volts

-usually lower current

4 benefits of batteries

-portable

-no cables

-safer (lower voltage)

-works in a power cut

Direct current graph

what is rectification

A process of converting AC to DC - usually reducing voltage supply

4 products that use a power supply that needs rectification

-laptop

-battery charger

-tv sets

-mobile phone

monostable switch

one stable state

has to be held

stable state is off

bistable

two stable states

stays where you left it

stable states are off and on

3 examples of a monostable switch

-doorbell

-keyboard

-tv remote

2 examples of a bistable switch

-lightswitch

-plug socket

Whats a relay?

a form of switch that is operated by magnetism rather than a physical touch or push

2 reasons to use a relay

-to operate a higher voltage circuit from a lower voltage circuit using magnetism

-different current needs

how does a relay work

when the electromagnet in the relay has enough current flowing through it the magnet turns on, pulling the switch across and completing the circuit. It is an interface between 2 circuits.

3 types of energy produced by outputs

-light

-sound

-motion

solenoid

same as a relay but rod moves in and out instead of a switch being pulled across

motor

turns electrical energy into rotational energy

bell

create a sound through the use of an electromagnet. use mechanical movement to hit bell

buzzer

predesigned sound, frequency cannot be changed

lamp

creates light, producing an analogue signal. Current passes through the filament, heating and lighting it up. Inefficient so LEDs are better