Explain the use of capacitor in time delay circuits?What is its definition? I don want to go deep into it Just keep it simple Please just for a 10 class student
1 Answer
The current into the capacitor is limited by an inline resistor. Therefore the time required for the voltage difference across the capacitor terminals to reach a desired level is increased.
Explanation:
Note: There is an analogy about filling a bathtub in the last 2 paragraphs.
Remember that current is measured in Amps and that 1 Amp is equivalent to
If you put a resistor in the path to a capacitor, the current flowing into the capacitor will be decreased (compared to having no resistor). The voltage across the capacitor increases as the number of Coulombs reaching the capacitor increases. So the voltage increases with time. Therefore the affect of the resistor and capacitor working together is that it will take longer for the voltage across the capacitor to reach its final value and be fully "charged".
To briefly describe how a timer works, imagine that the increase of voltage across the capacitor is monitored by a circuit to determine the moment that a certain voltage has been reached. Assume that certain voltage is 80% of the final voltage it will eventually reach. The value of the resistor and the capacitor can be adjusted to adjust the time delay for the voltage to reach 80%.
This is very similar to the situation of filling a bathtub. Assume it takes 3 minutes to get the water level up to a desired level with the faucet full on. If you close the faucet halfway, it might take 5 minutes to get the tub equally full. That faucet is like the resistor.
What if you swapped out the tub, getting a longer wider tub but used the old faucet? You would still want the water to be equally deep. That would take more water and more time than it did with the old tub. The tub's size is like the capacitor's capacitance -- a capacitor with more capacitance would require more Coulombs before the voltage reached the "trip" level.
I hope this helps,
Steve
