Electricity Flashcards
what is electric current?
the rate of flow of charge
or
how much charge flows per second
what are the symbol and units for electric current?
I
measured in amps (A)
what is the formula for current?
current = charge (c) / time (s)
charge measured in coulombs and time in seconds
why is charge the same value anywhere around a circuit?
charge is not used up by the components in a circuit (because energy can only be converted) so the amount of charge is the same anywhere
what is voltage and what is it measured in?
the amount of energy converted per coulomb of charge flowing
measured in joules
so 1 volt is really 1 joule per coulomb
what is the formula for voltage?
voltage = energy converted / charge flowing
what is resistance?
a measure of how difficult it is for electric current to flow
a property of an electrical component
what is the formula for resistance?
voltage (v) = current (A) x resistance (Ω)
what is Ohm’s law?
“voltage across a component is directly proportional to the current provided the temperature of the component doesn’t change”
what is the voltage equation?
voltage = energy converted / charge flowing
what is power?
the amount of energy converted per second
measured in Watts
if a bulb is 36 Watts, what does this mean?
the bulb converts 36J of energy per second
what is the power equation?
power = energy / time P = E/t
what is the electrical power equation?
electrical power = voltage x current?
P = VI
what is the purpose of a fuse?
to stop a current flowing when a fault occurs
how does a fuse work?
the large current will cause the fuse wire in the fuse to melt
the circuit will be broken
what does the earth wire do?
the earth wire is connected to the casing of a device (but only if the casing is metallic)
if a fault develops and the case becomes live, a huge current will flow down the earth wire into the ground
the current will flow through the fuse and melt it, thus breaking the circuit
what devices need earth wires and what is the name and symbol of a device that doesn’t require earthing?
devices with metal casing need an earth wire ie a kettle
devices that don’t require an earth wire are called “double insulated” and are stamped with this symbol
[■]
how can you identify the live wire in a plug?
the live wire is brown and will be attached to the fuse. it carries the current to the appliance
how can you identify the neutral wire in a plug?
the neutral wire is blue and will not be attached to the fuse.
it carries the current away from the appliance and completes the circuit
how can you identify the earth wire?
the earth wire is green and yellow
what is the name of the plastic bridge that holds the wire in place in a plug
the cable grip
