Everything Flashcards
What is an LDR
Light Dependent Resistor : component where resistance varies with light intensity e.g vehicle headlights
What is a thermistor
Component where resistance varies with temperature e.g digital thermometers, fire alarms
What do the LDRs and Thermistors have in common
As heat/light increases so does the resistance ( directly proportional )
Units for charge flow
Coulombs
Units for current
Amperes
What do step up transformers do
- increase p.d
- decrease current
Why is less current good for step ups?
- Less current means less heat generated
- Less heat lost by dissipation
More efficient
What do step down transformers do
- decrease p.d
- increase current
- power is restored for domestic and commercial use therefore much safer
Direct current
Current that flows in one direction only ( from cell/battery )
What is a.c
Current that switches directions around a loop ( from the mains )
What frequency is the Uk mains
50hz
What is the p.d in the sockets
230v
What is a d.c generator called and what does it do
Dynamo, produced positive cycles to be shown on an oscilloscope
What is an a.c generator called and what does it do
Alternator, used in power stations to generate huge amounts of electricity
How does a power station work basic
A rotating drum of magnets induces a current in stationary coils
What does live do
- Alternates between positive and negative current
- connected via a fuse within the plug to a device
What does neural do?
- Remains at 0v ( practically )
- acts as the completor for the circuit to do a whole loop
What does the earth wire do
- Only carries current is the device is faulted and the metal casing has a current flowing from the live
- carries the current from the metal out casing back to the power supply
Equations for frequency
Frequency = 1/ time period ( time for one oscillation)
Equation for power in a component
Power = current * p.d
( w )
What is power
The power of a device is the rate at which it transfers energy. Therefore the amount of energy transferred in an amount of time
What is 1w equal to
1 joule per second
What is the equation for power in a device?
Power = energy transferred / time taken
( in joules ) ( s )
