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Electricity

Mains Electricity - Alternating Current.

What does Alternating Current look like on a CRO?

If an alternating current supply is connected
to a cathode ray oscilloscope (called a CRO),
the display shows a wave as the current changes
from maximum positive to maximum negative.

The picture above shows two complete cycles
of the wave displayed on the CRO.
Where the wave goes above the zero line,
the current flows forwards.
Where the wave goes below the zero line
the current flows backwards.

The frequency of the alternating current can
be calculated from the period of the wave.

What does Direct Current look like on a CRO?

If a direct current supply is connected to the CRO,
the display shows a single straight line.
This is a constant current in one direction only.

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