P4.2 - Current And Charge (Finished) Flashcards
What is an electric current?
An electric current is the flow of electrical charge (carried by electrons)
Why can a current only flow if there is a source of potential difference?
Electric charge will on,y flow round a complete circuit if there is a potential difference, so a current can only flow if there is a source of potential difference
What is current measured in?
A, Amps
What is potential difference measure din?
V, Voltz
What is resistance and what is it measure din?
Resistance is anything that slows the flow of electric charge down. Measured in ohms
What does current flowing through a component depend on?
- The potential difference across the component
- The resistance of the component
The size of a current is the ___
Rate of flow of charge
What is the equation for charge flow?
Charge flow = current * time
What unit is charge flow measured in?
C, coulombs
What does a switch do?
A switch enables the current in a circuit to be switched on or off
What does a resistor do?
A resistor limits the current (by resisting the floe of electrons)
What is a variable resistor?
A resistor that you can vary
What does a fuse do?
A fuse breaks the circuit if the current is too high
What does a thermistor do?
A thermistor decreases in resistance as temperature increases?
What does a light dependant resistor do?
An LDR decreases in resistance as light intensity increases
What does a voltmeter do?
A volt meter measures potential difference across component(s)
What does an ammeter do?
An ammeter measures electric current
What does a diode do?
A diode only lets current flow in one direction
What does a light emitting diode do?
An LED is a diode that emits light when current is flowing the right way
What does a lamp do?
A lamp/bulb emits light when a current flows through
What is a battery?
A battery is multiple cells connected together
What is ancell?
A cell provides current to a circuit and energy to each charge (electron)
Why does a closed circuit with a battery have a current flowing through it?
Electric charge will only flow round a closed circuit if there is a potential difference. The battery provides the potential difference needed
