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What is Electric Current?

Current is
the "rate of flow of coulombs"
in

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
by",

so current = charge
÷
time. I = Q
÷ t.

We can calculate the current
if we know

the charge and the time.

This equation
can be
rearranged to give

charge = current x time.
Q = I x
t.

Current
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.

Current
has a heating
effect

and thick
wire must be used to carry a large current.

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