﻿ Time constants, capacitors charge and resistance. - Attractive and easy to follow guide for students needing basic electronic guidance. Worked example for calculating a simple time constant using a capacitor and a resistor in an electronic circuit.
14th  November 2010
Capacitors are used in circuits to store electrical charge for a short time.  They can be either polarised or non-polarised, which mans either that they have to be connected the right way round (like the LED) or you can connect them anyway you like.. (like the resistor).  If a capacitor is polarised it has a slightly different symbol on the circuit diagram and it is marked on the case with a plus-sign (+) or a minus sign (-)
A non- polarised capacitor is shown with just two similar filled-in boxes
Think back to when you were first told about resistors and electricity and you may have been told to think in terms of water flow, perhaps from a tank or reservoir.  The resistor restricts the flow of the electricity in a circuit in the same way as water is restricted when a tap is turned half-off.
Increasing the value of the resistor will lengthen the time …..or increasing the amount of charge in the capacitor (raising the value of the capacitor) could do the same thing.
CAPACITORS have values that are measured in FARADS.  The FARAD is a very large unit and so more frequently capacitors have values measured in MICROFARADS ( millionths of a farad )