P2 Electricity Flashcards
What does a fixed resistor do
Limits the current in a circuit
What does a variable resistor do
Allows the current in a circuit to be varied
What does a thermistor do ?
Allows the current depending on the temperture
What does a fuse do ?
A fuse is designed to melt and break the circuit if the current is too great
What does a cell do
It pushes the elctrons around a complete circuit
What does a switch do
A switch enables you to break and complete a circuit , so turn on and off
What does a bulb do
A bulb emits light when current passes through it
What does a diode do ?
A diode allowes current through in only one direction.
What does a LED do ?
Emits light when the current passes through it
What does a LDR do ?
Decreases in resistance as light intensity increases
What does an ammeter do ?
Used to measure the elctric current ( amps )
What does a voltmeter do ?
Used to measure the electric potential difference
What is electric current
A flow of electrical charge
Current is measured in
Amperes
Charge is measured in
Coulombs
What is the potential difference
It is the “driving force “ that pushes charge around the ciruit
What ia resistance
Anything that slows down the charge
Formula linking charge flow, current and time
Charge flow = current x time
The greater the resistance acroos a component the
Smaller the current that flows
What are ohmic conductors
Components with a fixed resistance ( resistance won’t change with current )
Examples of ohmic conductors
Wires and resistors
Some components however do have changing
Resistance
Example of components with changing resistance
Filament lamp or a diode
The resistance increases with
Temperature
What is an IV characteristic
A graph showing how the current flowing through a component changes as the potential difference across it changes
Where are thermistors used ?
Used in car engines and central heating thermostats
Where is a LDDR use ?
Automatic night light or outdoor lighting.
In a series circuit the components are all connected
In a line between the ends of the power supply.
In a series circuit if you remove one component then
The circuit is broken, so all components stop working
In a series circuit the total potential difference is shared
Between all of the components
In a series circuit if you dd all the potential difference of each component you will get the
Potential difference of the power supply
Inna series circuit the total resistance of two components is found by
Adding up their resistance
