Electricity

Created by

Lorelie

Cards (72)

What is current
Flow of electrical charge
When can current flow
when there is a potential difference
What is the unit for current
ampere
What is potential difference
The force that pushes the charge around the circuit
What's the unit for potential difference
Volt
What is resistance
Anything that slows down the flow of charge
What's the unit for resistance 
Ohms
What does the current flowing through a component depend on
The potential difference across it and the resistance of the component.
What does a greater resistance cause
A smaller current
What is the size of a current
The rate of flow of charge
What is an ohmic conductor
The resistance doesn't change with the current
How can the current in an ohmic conductor be described
Directly proportional to the potential difference (at a constant temperature)
What happens when electrical charge flows through a filament lamp
Some energy is transferred to the thermal energy store of the filament
Resistance increases with temperature
More current=filament heating up more=higher resistance
What happens when electrical charge flows through a diode
The resistance depends on the direction of the current
Current can flow through one direction but there's a very high resistance if its reversed
What is an I-V characteristic?
A graph which shows how the current flowing through a component changes as the potential difference across it is increased
What's the I-V characteristic of a linear component
A straight line
What's the I-V characteristic of a non linear component
Curved
What is a LDR
Light dependant resistor
What happens to an LDR in bright light
Resistance falls
What happens to an LDR in darkness
Resistance is higher
What are applications of LDRs
Automatic night lights, outdoor lighting and burglar detectors
What is a thermistor?
A temperature dependant resistor
What happens to thermistors in hot conditions
Resistance drops
What happens to thermistors in cold conditions
Resistance increases
What are thermistors used for
Car engine temperature sensors and electronic thermostats
What can sensing circuits be used for?
To turn on or increase the power to components depending on the conditions that they are in
Describe a series circuit
All components are connected one after the other. If one breaks, charge stops flowing.
Describe potential difference in series circuits
It's shared between the components
Potential difference around a series circuit will always add up to the source of pd
Describe the current in a series circuit.
Current is the same everywhere
What happens when you add a resistor in series
The resistors have to share the total pd
What happens to the total current in a series circuit when a resistor is added
It's reduced
What happens if you remove or disconnect a component in parallel circuits
It will hardly effect the other components
Describe potential difference in parallel circuits
All the components get the full source pd
Describe current in parallel circuits
The total current is equal to the total of all the currents through the separate components
What happens when you add a resistor in parallel
It reduces the total resistance
Why does adding a resistor in parallel reduce the total resistance
-both resistors have the same potential difference across them
-by adding another loop the current has more than one direction to go in
-this increases the total current that can flow round a circuit
-increase incurrent means decrease in resistance
What is alternating current
The current is constantly changing direction
they’re produced by alternating potential differences in which the positive and negative ends keep alternating
what is direct current
A current that’s always flowing in the same direction, its created by a direct potential difference
what’s the uk mains supply pd and voltage
230v
50hz
what current do cells and batteries supply
direct current