electricity

current symbol

I

current unit

A

potential difference symbol

V

potentially difference unit

V

resistance symbol

R

resistance unit

ohms

open switch

for charge to flow THE SWITCH MUST BE CLOSED

closed switch

cell

battery

diode

resistor

variable resistor

LED

Lamp

fuse

voltmeter

ammeter

thermistor

LDR

diode?

only allows current in one direction

LDR?

resistance decreases as light increases

thermistor?

TURD

temp up, resistance down

current in series circuit

same everywhere

current in parallel circuit

split (NOT EQUALLY) unless the resistance in each branch is the same.

potentially difference in series circuit

shared between components

potential difference in parallel circuit

same across every branch

resistance in series circuit

total = sum of all the resistors.

not equal

resistance in parallel circuit

total resistance is LESS THAN the smallest resistor

UK voltage

230V

RP: factors affecting resistance

• set up a circuit with a battery, ammeter, and a long piece of wire clamped to a meter ruler

• attach a crocodile clip at 0cm and another at 10cm

• record the current from the ammeter

• record the potential difference from a voltmeter, placed in parallel across the test wire

• move the crocodile clip to diff distance on the ruler and record the V and I at each step

• calculate resistance for each length using R = V/I

RP: I-V characteristics

• set up a circuit w a battery, ammeter, variable resistor and (the component ur testing)

• use the variable resistor to change the potential difference across the component

• take readings of V and I

• switch direction of battery to get negative values for V and I

• repeat for a fixed resistor and a diode

resistor graph

filament lamp: resistance increases as temp increases

diode graph

UK frequency

50Hz

live wire (brown)

carries the 230v alternating potential difference from the supply.

dangerous to touch

neutral wire (blue)

completes the circuit

its at 0V

earth wire (green/yellow stripes)

safety wire

only carries current if theres a fault

stops the exterior of an appliance from becoming live

national grid

1) power stations:

• generates electricity at a relatively low V

2) step up transformer:

• increases the V and decreases current

• high current = wire heats up (dissipation)

3) long distance transmissions:

• how the electricity travels across country

4) step down transformer:

• decrease V and increase current

• for costumer safety

5) houses