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