current and circuits Flashcards
what is current and unit
flow of electric charge (electrons) around a circuit
unit - amp (a)
what is potential difference (pd) and unit
pd is energy transferred per unit charge
unit - volt (v)
what is resistance and unit
anything which slows down flow
unit - ohm
charge equation
current x time
name all the circuit symbols
- cell
- battery
- open switch
- closed switch
- filament lamp
- fuse
- LED
- power supply
- resistor
- variable resistor
- ammeter
- voltmeter
- diode
- LDR
- thermistor
- motor
energy transferred equation
charge moved x potential difference
what usually happens to resistors and why
increase with temperature as a charge flows through as it has to do work against the resistor. this is due to electrons colliding and vibrating which heat up.
what is an ammeter
measures current flowing anywhere in the circuit
what is a voltmeter
measures potential difference across a component
how to investigate diodes
remove diode and swap its direction, current can no longer flow through
how to investigate thermistors
gradually heat it while keeping pd the same, temp should increase as resistance increases
how to investigate LDRS
in a dim room, keep pd the same and slowly adjust light level near the LDR. light level should get brighter, current increases and resistance decreases.
resistor and wires graph
current is directly proportional to pd, all different slopes
filament lamp graph
increasing current increases temp, graph is curved
diode graph
current only flows one direction, high resistance in opposite direction
