P2 - Electricity Flashcards
What is electric current
Is a flow of electrical charge
Electrical charge will only flow round a complete circuit if something is
Providing the potential difference
What is the potential difference
The potential difference is the “ driving force “ that pushes charge around the circuit
What ia resistance
Anything thst slows down the flow of charge
The current flowing through a component depends on the potential difference across it and the resistance of the component
The greater the resistance across a component, the smaller the current that flows
Components with a fixed resistance are called
Ohmic conductors
What is a fixed resistance
The resistance of the component doesn’t change with current
Ohmic conductors only have a fixed resistance if the
Temperature doesn’t change
Examples of ohmic conductors
Wires and resistors
For an ohmic conductor at a fixed temperature , the current flowing
Is directly proportional to the potential difference across it
However the resistance of some components does change with current E.g.
A diode
The resistance of an LDR changes as the intensity ofmlight changes .In bright light
The resistance isnlow and in darkness the resistance is high
What is a thermistor
A temperature dependent resistor
What are sensing circuits
Can be used to automatically change the pd acroos components depending on changes in the environment
What is 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
The circuit is broken.All the componennts stop working
In a series circuit the same current flows
Through all components
In a series cirxuit the total potential difference is
Shared between all components .If you add up the pd across each component you will get the pd of the power supply
In parallel circuits, each component is separately
Connected to the ends of the power supply.If you take out one loop, the things in the other loops won’t be affected .This means things in parallel cidxuits can be switched on and off without affecting each other
In a parallel circuit , all components get the full
Potential difference.Potential difference the same everywhere
What is an alternative potential difference
Is a potenial difference that is constantly changing direction.It produces an alternating current
In an alternating current the current
Is also constantly changing dkrection
What is the brown wire
The live wire
What is the live wire
The live wire provides the alternating potenital difference from the mains supply
What is the green and yellow wire
The earth wire
What is the earth wire
Earth wire is the safety wire.Stops the appliance becoming live.It is connnected to the metal casing of an appliance.If a fault causes the live wire to touch the casing , the current flows away through the earth wire
What is the blue wire
The neutral wire
What is the neutral wire
Neutral wire completes the circuit.When the appliance is operating normally , current flows through the live and neutral wire
What is the National Grid
The national grid is a giant system of cables and transformers that covers the UK.It transfers electrical power from power stations to consumers
Step up transformer
Increases the voltage and reduces the current
Step down Transformer
Reduces voltage and increases the current
