The Transformer Equation.

This equation is important!

The transformer equation
relates the

number of turns of wire
to the difference in voltage

between the primary and
secondary coils.

^{V}^{p}/_{Vs} =
^{Np}/_{Ns}

Where Vp is the
voltage in the primary coil.

Vs is the voltage in the secondary coil.

Np is the number of turns of
wire on the primary coil.

Ns is the
number of turns of wire on the
secondary coil.

There are two points to remember.

1.
Transformers only work with alternating
current.

Using direct
current will create a magnetic
field in the core

but it will not be a changing magnetic field

and so no voltage will be induced in the secondary coil.

2.
Using a step
up transformer to increase the voltage

does not give you something for nothing. As the voltage

goes up, the current goes
down by the same
proportion.

The power equation shows

that the
overall power remains the same,

P = V x I Power = Voltage x Current.

In reality, the output power is always less than the
input power

because the changing magnetic field in
the core

creates currents (called eddy currents) which heat the core.

This heat is then lost to the environment, it is wasted
energy.

Links Electromagnetism Transformer Revision Questions

gcsescience.com Physics Quiz Index Transformer Quiz gcsescience.com

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