# Physics- Ac circuits

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• Created by: FireDwarf
• Created on: 23-11-13 12:09
What is a ac current?
An ac current is when a current repeatly reverses its direction. In one cycle, the carrier moves one way in the circuit and then reverse direction then re-reverse direction.
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What is the freqency?
The number of complete cycles it passes through each second (hz)
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Peak value?
Maximum current/pd which is the same in either direction.
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What does time period mean?
Time for one complete cycle.
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Why do we use ac?
Because a larger V is more efficent then larger current because less power is dissipated.
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What is the freqency and mean voltage of the UK?
50hz and 230V
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What does RMS mean?
It is the root mean square value and is the value of DC current that would give the same heating effect as the AC in the same resistor.
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What are the formulas for RMS?
Prms= Po (Peak Power)/ square root of 2 (same for Irms) Power = Irms(^2)R, Vrms = Irms x R
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heating effect of an AC current?
an electric heater at a very low frequency would be going cold then hot then cold then hot due to the alternating current (switching directions).
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How does an ossiliscope work?
Electron gun emits an electron at a flurescent screen. Posistion of the spot of light is effected by the P.D across either of the deflecting plates. With no pd, the spot remains in the same space. Displacement is proportional to the applied p.d
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Therefore how can it be used as a volt meter?
As the displacement of the beam is proprotional to the p.d applied.
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## Other cards in this set

### Card 2

#### Front

What is the freqency?

#### Back

The number of complete cycles it passes through each second (hz)

Peak value?

### Card 4

#### Front

What does time period mean?

### Card 5

#### Front

Why do we use ac?