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Level Physics Notes: Electricity – Tesla Coils
Basic Tesla coil theory involves the
property of resonance. When a coil and capacitance are connected in
parallel and briefly pulsed with a voltage, the discharge flows back
and forth between the two at a frequency that depends on the values
of both, until dissipated by the resistance of the two. Change the
value of either one and the resonant frequency changes. In a Tesla
coil, there are actually two resonant circuits connected together.
One, between the capacitor and the primary, the other between the
secondary and the same capacitor.
As
the potential across the gap increases, the charge across the
capacitor also increases. When the gap breaks down, meaning the
charge across it is sufficient for electrons to jump across, it
sparks and causes the capacitor to discharge through the primary.
This discharge then resonates back and forth through the primary and
to alternate plates of the capacitor until the charge across the gap
builds up again. Since the secondary is also connected to the
capacitor, the secondary also resonates. When the frequency of the
capacitor and primary circuit resonates at the same frequency as the
capacitor and the secondary, the voltages add, and the output goes up
through the roof. The frequencies involved are in the hundreds of
thousands of Hz, and the voltages can reach into the hundred
thousands or even millions of volts.
The effect can be stunning.
