I have connected a variable capacitor and a LED in series with a DC 9V source. When I vary the capacitor , the brightness of the LED changes. But how it happens?

 

I have connected a variable capacitor and a LED in series with a DC 9V source. When I vary the capacitor , the brightness of the LED changes. But how it happens?

The capacitor will conduct until it's charged. Post a schematic for a better answer.

 

I have connected a variable capacitor and a LED in series with a DC 9V source. When I vary the capacitor , the brightness of the LED changes. But how it happens?

Means that the variable capacitor is shorted. Test it with an Ohmmeter.

 

Your 9V source may be pulsing, and the capacitor can pass current will charging. But you'd need a large capacitor for this. Mike's answer seems more likely.

 

Your 9V source may be pulsing, and the capacitor can pass current will charging. But you'd need a large capacitor for this. Mike's answer seems more likely.

no, its just a 9V battery

Your 9V source may be pulsing, and the capacitor can pass current will charging. But you'd need a large capacitor for this. Mike's answer seems more likely.

 

I have connected a variable capacitor and a LED in series with a DC 9V source. When I vary the capacitor , the brightness of the LED changes. But how it happens?

Which capacitor was that GANG?

 

I think there is 9-volt battery and connect to a 470Ω resistor which is in series with a 100K potentiometer connected to an LED. We use a protection diode in this circuit so that if the 9-volt battery is inserted the wrong way, the LED can be protected from reverse current.

 

I have connected a variable capacitor ...

So it's really a variable resistor, not a capacitor?

 

no, its just a 9V battery

Make it easier for us to help you. Post a schematic of your circuit and a picture of your variable capacitor. How do you expect to limit LED current?