Volts
Energy is measured in Joules.
The power
supply (the cell or battery) gives an amount of energy
to each
Coulomb going
around an electric circuit.
A 6 Volt
cell gives 6 Joules of energy to each Coulomb.
1 Volt = 1 Joule per Coulomb.
The word "per" means "divided
by",
so Voltage = Energy ÷
Charge.
This can be
rearranged to give
Energy = Voltage x
Charge. E = V x
Q.
Since Q =
I x t,
if we write I x t
instead of Q in the above equation we get
E = V x I
x t. Energy = Voltage x current
x time.
(see
equations).
We can also write Work
instead of Energy, so you might see one of the
above equations written as Work
= Voltage x
Charge. W
= V x
Q.
Voltage (which is also called
potential difference, or p.d.)
is an electrical pressure pushing
current around a circuit.
Doubling
the voltage will double
the current.
Voltage is measured using a voltmeter.
The voltmeter, shown as a circle with the letter
V inside,
is always connected in parallel with the component.
(The voltmeter is said to be connected
across the component,
where the word "across" means
"in parallel with").
The circuit on the left would show the voltage of the cell.
The circuit on the right
shows the voltmeter connected
across a lamp.
This will tell you how many Joules of
energy are being converted
from electrical energy into
light energy (+heat)
for each Coulomb which passes through
it.
A reading of 6 Volts tells you that 6
Joules of energy
are being converted for each
Coulomb passing through the
lamp.
A reading of 10 Volts tells you that 10
Joules of energy
are being converted for each
Coulomb passing through the
lamp.
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