science notes chapter 13 - electrical systems

ammeter

measures the current flowing through an electric component

to be connected in series

voltmeter

measures the potential difference across an electrical component

to be connected in parallel

current

the rate of flow of electric charge

SI unit for current

ampere A

resistance

a measure of how much the component opposes the flow of electric current

fixed resistor

connected in a circuit to provide a constant resistance, which limits the current so that components do not overheat or get damaged.

variable resistor

connected to the circuit to enable us to change resistance this will change the current flowing through

symbol for fixed resistor

symbol for variable resistor

si unit for potential difference

voltage v

formula for total resistance in series

R1 + R2 + R3….

formula for total resistance in parallel

(R1 + R2 +R3…) to the power of negative 1

formula for electricity

SI unit for resistance

Ohm

live wire

The live wire carries the current from the power supply (mains) into the electrical appliance

neutral wire

connects the appliances back to the source in order to close the circuit for the object to work

earth wire

a safety feature that is usually connected to the metal casing of appliances. it helps prevent electric shock by diverting current into the ground when the live wire touches the metal casing

fuse

safety device added to an electrical circuit to prevent excessive current flow . it will blow up when the operating current exceeds its current rating

symbol for fuse

features of series circuit

current flowing through each resistor is the same as total resistance

potential across each resistor added up is the total emf of cell

lightbulbs in series

removing one lightbulb will result to other lightbulbs not lighting up due to an open circuit

features of parallel circuits

current in each resistor adds up to total current

potential difference is constant for all resistors in the circuit

effect of adding more lightbulbs in parallel

each lightbulb will still remain the same brightness

removing one lightbulb in parallel

other bulbs remain lit

SI unit for power

watt w

power

the rate of energy converted into other forms

formula for electrical energy consumption (energy)

power x time

si unit for electrical energy consumption

kWh

formula for cost

energy x cost per kWh