3. HISTORY OF ALTERNATING CURRENT
William Stanley, Jr. designed one of the first practical devices
to transfer AC power efficiently between isolated circuits.
The AC power system used today developed rapidly after 1886,
and included contributions by Nikola Tesla and Carl Wilhelm Siemens.
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4. WHAT IS ALTERNATING CURRENT ?
Alternating current electricity is the type of electricity commonly used
in homes and businesses throughout the world.
AC electricity is created by an AC electric generator, which determines
the frequency.
An AC waveform can be sinusoidal, square, or sawtooth-shaped.
Some AC waveforms are irregular or complicated.
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5. Alternating current flows first in one direction and then in the other
direction.
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6. ADVANTAGES
The single greatest advantage of alternating current is that AC current
can be transformed and DC current cannot be transformed.
It can be controlled by a wide range of components
eg.resistors,capacitors and inductors.
This allows high-voltage electrical power to be distributed with smaller
wires and lower amperage.
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9. RMS VALUES
Since voltage and current are always changing we need some way of
averaging out their effect.
We use r.m.s values (root-mean-square)
The r.m.s values are the DC values which give the same average
power output
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11. AC IN CAPACITORS
In an AC circuit, the current can continue to flow, as the plates
become alternately charged positively and negatively
For both AC and DC circuits, the voltage across the resistor is
related to the current by V=I.R
A similar relationship exists for a capacitor:
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12. REACTANCE
Reactance is a measure of how a capacitor can limit alternating
current.
It is similar to resistance but differs in that it is dependent on the
frequency of the ac supply.
It also depends on the size of the capacitor.
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14. AC IN INDUCTORS
.In an AC circuit, the current is always changing so the inductor is always producing an
opposing voltage so is always limiting the amount of current that can flow
For both AC and DC circuits, the voltage across the resistor is related to the current by V=IR
A similar relationship exists for an inductor
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15. REACTANCE
It measures how well an inductor can limit alternating current
It depends on the frequency of the ac supply.
It depends on the size of the inductor
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