it was said by my friend that capacitor cant discharge with out resistance in series. How far it is right?

Answer 1

Well, let's imagine that we short circuit the terminals of the capacitor with a perfect wire (zero resistance). This creates a simple RC circuit where the time constant equals zero. This means that all the energy in the charged capacitor is dissipated within a very short amount of time.

While it is possible to discharge a capacitor without a resistor in series, this isn't always desirable. Anybody that has shorted a charged cap with only a wire knows that there is usually a loud snap accompanied by a spark, and the terminals of the cap can be locally burned. The more civilized way to go about discharging a capacitor is to find a resistor that will discharge the capacitor in a longer amount of time. I usually shoot for a time constant (R*C) of about a few seconds or so, which means the cap will be close to fully discharged after 10-15 seconds without any spark or snapping sound. Leaving the terminals open-circuited will leave the capacitor charge forever theoretically, but in practice there is always a certain amount of leakage.

Answer 2

Your friend is wrong. You can prove this to him by charging a small electrolytic capacitor with a small resistor on its (-) (this prevents from discharging on its own). Then turning off its power source. Remove the ecap from the resistor and everything else. Now SAFELY touch the (+) and (-) on the ecap together. See that spark?? Thats the ecap discharging. There was virtually no resistance there either.

A capacitor is used in conjuction with a resistor to slow down the discharge. Thats why the simplest timing circuit uses a capacitor and a resistor.

P.S. when you say resistance do you mean a resistor? because everything EVERYTHING has some amount of resistance.

Answer 3

The dicharge time of a capacitor is known as time constant tau.
tau = RC where R = Resistance and C = Capacitance
The larger resistor or capacitor we have the discharge time is longer. If there is no resistance, it's like charging a capacitor and letting it set there. In theory, the capacitor is suppose to store that energy for infinite amount of time. But due to lickage, the capacitor will discharge eventually and go back to original state. Thus your friend is correct!

Answer 4

A capacitor can be discharged without a resistor - it is safer to discharge it with a resistor otherwise depending on the size of the capacitor you can weld the contacts to the discharge wire and even damage the capacitor.

Answer 5

Flase, the capacitor can discharge without a resistance in serce. The resistance only slow or increase the rate of discharge.

Answer 6

Capacitors usually are intentionally discharged by placing a resistor across their leads.All capacitors will "leak-down" over time.Some take longer than others. Always use care when handling/working around them! The bleed capacitor in a microwave oven,for example,holds 600-800volts! :-)=

Answer 7

p0 is correct.

The discharge time constant is the product of the capacitance and the resistance. If you have 0 resisitance then the capacitor would instantaneously discharge. Now, is that physically possible? That's a whole different topic.

Answer 8

Even when you short a charged capacitor there is always a small amount of resistance in series even if it is only a few micro or milli ohms.

Answer 9

There is no such as a perfect capacitor that can hold a charge forever. All of them will discharge over a period of several days or weeks.

Answer 10

The resistance value in series determines how quickly the cap discharges.