Usually the value of Capacitor is printed on its body. In Disc and Polyester capacitors, the value is indicated in PF, uF etc or as EIA code. But in some capacitors, the value is represented as coloured rings as in the case of Resistor. The value can be determined using the standard resistor colour code chart. Tantalum bead capacitor is identified in a different way with colour code.
Inside the Capacitor
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
Value is marked on the capacitor directly or in colour codes
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
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
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)
Tantalum bead capacitor
Tantalum capacitors are reliable and accurate in performance. So it is used in circuits using frequency generation, timing etc. Unlike other capacitors, leakage is practically nil in Tantalum capacitors.
The ordinary Tantalum capacitor has its value printed on its body, but some Tantalum capacitor uses colour code.
From the upper end, the first two colour bands are significant representing the value in uF and the dot represents the Multiplier. The third and lower most colour represents the voltage.