A Capacitor stores electric charge. Basically a capacitor consists of two metal plates separated by an insulating material called “dielectric”. When connected to a power source such as battery, the capacitor charges up until the potential difference between its terminals become equal to the e.m.f of the battery.
The capacitance of the capacitor is its ability to store charge and is measured in terms of Farads. The capacitance depends on the area of the plates and the distance between them and also the type of dielectric used.
Capacitance
= Q / V
Where Q is the
charge and V is the voltage.
Thus the capacitance is the charge divided by voltage.
The important parameters of the capacitor are
1.
Value
Value is marked on the capacitor
directly or in colour codes
2.
Tolerance
It indicates how much more or less the
actual capacitance of the capacitor
3.
Working
voltage
It is the maximum voltage a capacitor
can withstand before the dielectric breakdown
4.
Leakage
current
There is always small leakage current in
all capacitors. Ideally this should be zero. But no capacitor is perfect
without leakage current. Tantalum capacitor is comparatively better with
minimum leakage current
Colour coding
Like resistors, some capacitors are colour coded to indicate value, tolerance, working voltage etc. These colour bands are numbered from the top of the capacitor to the base. The colour coding is similar to
Resistor colour coding
Capacitor color code
- First band – First number of colour code chart
- Second band – Second number of colour code chart
- Third band – Number of Zeros
- Fourth band – Tolerance (Black 20%, White 10 % and Green 5 %)
- Fifth band – Appears as body colour. Working voltage (Red 250V, Yellow 400 V)
