Section 2 - Electricity Flashcards
current
rate of flow of charge (carried by electrons) in a circuit
(AMPS - A)
voltage
what drives current round circuit (also known as potential difference)
Volts - V
resistance
anything that slows flow down
ohm (Ω)
ammeter
measures current in amps flowing through a component
- must be placed in series
voltmeter
measures voltage (in V) across a component
- must be placed in parallel
mains supply
in uk 230v alternating current - so constantly changing direction
battery supplt
direct current - always in same direction
Voltage formula
V=IR
voltage = current x resistance
I-V graph
shows how current varies as you alter the voltage
I-V graph working out
gradient = resistance
steeper gradient = low resistance
straight line graph = constant gradient therefore resistance
wire i-v graph
/ shape
current through a wire at constant temp is proportional to the voltage
different resistors i-v graph
/ varying
current through a resistor at a constant temperature is proportional to voltage.
- different resistors have different resistances therefore slightly different slopes
metal filament lamp i-v graph
S kinda shape
as the temperature of the metal filament increases the resistance increases hence the curve
diode i-v graph
—l shape
current will only flow through a diode in one direction as shown
Light Emitting Diodes
indicate the presence of current in a circuit. (light up when current goes through in forward direction)
Often used by appliances to show that they are switched on and for digital clocks, traffic lights, and remote controls
advantages - no filament that will burn out
Light Dependant Resistor
a special type of resistor that alters its resistance depending on how much light falls on it
bright light - resistance falls
darkness - resistance highest
useful for electronic circuits like burglar detectors
Thermistor
temperature-dependant resistor
hot - resistance drops
cold - resistance builds
useful temp detectors for car engines, thermostats, and fire alarms
series circuits
- different components are connected in a line, end to end, between the +ve and -ve of power supply
- if you remove/disconnect one they all stop working (so impractical in reality)
series circuit Characteristics:
- there’s a bigger voltage supply when more cells are in series
- current is the same everywhere
- voltage is distributed between components according to their resistance
- total resistance is sum of resistance in each component
parallel circuits
each component is separately connected to +ve and-ve of the supply.
- if you remove or disconnect a component it will hardly affect the others
components on same branch share series rules
parallel circuits Characteristics:
- voltage is the same across all branches
- current is shared between branches
- total cuurent is the same as addition of current in separate components
- junctions - current either splits or rejoins (total current going in a junction = total current going out)
- current through a branch depends on resistance in branch
charge (C) through a circuit formula
current x time
Q = It
charge drps blah blah
energy transferred (J)
charge x voltage
E=QxV
or
charge x current x resistance
QxIxR