# How does a capacitor regulate voltage?Watch

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Thread starter 4 years ago
#1
In some of my edexcel A2 Physics unit 4 past papers, they ask about using a capacitor for regulating a varying voltage. The capacitor makes it more constant. How does this happen? What is the physics behind this?
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4 years ago
#2
(Original post by X3X4fr)
In some of my edexcel A2 Physics unit 4 past papers, they ask about using a capacitor for regulating a varying voltage. The capacitor makes it more constant. How does this happen? What is the physics behind this?
The output from a bridge rectifier looks like the bottom plot here.

it's DC because it always has the same direction - but it varies very regularly over time.

it wouldn't be suitable for a lot of applications - if you used it to power an audio amplifier it'd play a constant buzz through the speakers and be dreadful.

if you connected a large capacitor across the output of the rectifier, the voltage would be considerably smoothed as the capacitor would store the peak charge.

TBH I'd call it smoothing rather than voltage regulation - which was always something different when I was learning it - can you post the exact question.
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Thread starter 4 years ago
#3
(Original post by Joinedup)
The output from a bridge rectifier looks like the bottom plot here.

it's DC because it always has the same direction - but it varies very regularly over time.

it wouldn't be suitable for a lot of applications - if you used it to power an audio amplifier it'd play a constant buzz through the speakers and be dreadful.

if you connected a large capacitor across the output of the rectifier, the voltage would be considerably smoothed as the capacitor would store the peak charge.

TBH I'd call it smoothing rather than voltage regulation - which was always something different when I was learning it - can you post the exact question.
http://qualifications.pearson.com/co...e_20100618.pdf
question 16
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4 years ago
#4
That question is talking about smoothing - the capacitor stores charge from the rectifier and smooths out the voltage waveform.
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Thread starter 4 years ago
#5
(Original post by Joinedup)
That question is talking about smoothing - the capacitor stores charge from the rectifier and smooths out the voltage waveform.
So basically what happens is the capacitor starts discharging when the voltage starts to dip?
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4 years ago
#6
(Original post by X3X4fr)
So basically what happens is the capacitor starts discharging when the voltage starts to dip?

Source: Google Images (http://www.eleinmec.com/article.asp?19)
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Thread starter 4 years ago
#7
(Original post by Phichi)

Source: Google Images (http://www.eleinmec.com/article.asp?19)
Alright mate thanks!
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