Static and Current electricty Flashcards
Where charges come from
Rubbing materials does not create electric charges. It just transfers electrons from one material to the other.
Example of electric charges transferring
When a balloon rubs a piece of wool..
Electrons are pulled from the wool to the balloon.
The balloon has mor electrons than usual.
Balloon: negative charged
Wool: positive charge
Static electricity
A stationary electrical charge that is built up on the surface of a material.
insulator
material through which charge cannot flow
conductor
material through which charge can flow
electricity
electrons moving through a metal wire/circuit
current
movement of electrons
current measurement, symbol, how to measure
measurement: amps (A)
symbol: I
Measured using: ammeter
voltage
measure of push or force that a power supply has to drive a current
voltage measurement, symbol, how its measured
measurement - volts (V)
symbol - V
Measured using - voltmeter
resistance
ability of a substance to reduce current
resistance measurement, shmbol, measured using..
measured in: ohms (horseshoe symbol)
symbol: R
measured using: ohmmeter
average voltage in Ireland
230 volts
OHMS LAW diagram
diagram in hardback
ohms law
Voltage is directly proportional to current
direct current
pushes current in one direction only
eg. battery
alternating current
current which is consistently changing direction
eg. current from ESB
Why 2 LEDs would glow dimly if the battery was alternating current
current will only flow in current direction half the time, so LEDs will be dimmer
OHMs law triangle
Current (i) x Resistance (R)
two bulbs in series
If you remove one bulb, the other will not light,
Eg. christmas lights
two bulbs in parallel
if you remove one bulb, the other will stay lighting
eg. bulbs in your house, car lights
unit of electrical energy
kilowatt hour
kilowatt hour
energy used when 1 kilowatt of power is used for 1 hour
calculating cost of electrical appliances
no. of kilowatts x no. of hours = kilowatt hours
kilowatt hours x cost per unit = cost
wats to kilowatts
kilowatts = watts / 1000
watts = kilowatts x 1000
3 effects of electricity
heating effect,
chemical effect,
magnetic effect
everyday uses of heating effect
boil water in a kettle
immersion heater
electric cooker
fuse
a safety device
fuse purpose
limit size of current flowing in circuit
how a fuse works
when current flowing through plug is greater than current rating on fuse (eg. 13A) wire in fuse heats up + melts
breaks electric circuit, stops current flowing
everyday uses of chemical effect
electroplating
recharge battery (eg. mobile phone)
electroplating
expensive metal like silver is coated onto a less expensive metal
magnetic use everyday uses
electromagnet
circuit breaker
live wire
brown, on right
neutral wire
blue, on left
earth wire
yellow + green, middle
diodes and batteries
in hardback
forward bias
current flows.
eg
+ end of diode is connected to + terminal of battery
reverse bias
current does not flow.
eg
- end of diode is connected to + terminal of battery
what does LED stand for?
Light Emitting Diode
why LEDs are more efficient
require less current, less energy is lost as heat
LEDs
give out light when current flows through them
only emit light if it is in forward bias
resistor must be connected in series to limit current (too much burns out/damages LED)
everyday applications of LEDs
Red light on electrical appliances - standby mode light on TV
Cyclists use LED lights
LDR - what does it stand for
Light Dependent Resistor
LDRS
resistor whose value of resistance can change as the intesnity of the light falling on it changes
LDRS - bright light
resistance low
large current flows
LDRs - dim light
resistance high
small current is flowing
everyday applications of LDRs
light meter on camera - amount of light entering camera controls resistance of LDR, changes setting of camera
street lights
-darkness - resistance of LDR imcreases, actives control circuit to switch on light
measure resistance of LDR with varying degrees of brightness
diagram in hardback,
result: value of resistance increased as brightness of bulb decreased.
