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What is Electric Current?
the "rate of flow of coulombs"
an electric circuit. A coulomb is a unit of charge,
so an electric current is a flow of charge.
Charge is given the symbol Q.
Current is given the symbol I.
This is the capital letter I, not a number 1.
Current is measured in amps.
What is an Amp?
1 amp = 1 coulomb per second.
The word "per" means "divided
so current = charge ÷ time. I = Q ÷ t.
We can calculate the current
if we know
the charge and the time.
rearranged to give
charge = current x time. Q = I x t.
can also be calculated using
I = P ÷ V and I = V ÷ R
See all equations for electricity.
How is Current measured?
Current is measured using an ammeter.
The circuit diagram above shows how to measure
the current flowing through a lamp. The circuit symbol
for an ammeter is a circle with the letter A inside. An
ammeter is always connected in series with a component.
If the ammeter reads 1 amp,
then the current (I) = 1 amp at that point in the circuit.
I = 1 amp = 1 coulomb per second.
If the ammeter reads 6 amps,
then I = 6 amps = 6 coulombs per second.
has a heating
and thick wire must be used to carry a large current.
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