Superconductors
When few metals are cooled, then below a certain critical temperature their electrical resistance suddenly becomes zero. In this state, these substances are called superconductors and this phenomena is called superconductivity.
Mercury become superconductor at 4.2 K, lead at 7.25 K and niobium at 9.2 K
Colour Coding of Carbon Resistors
The resistance of a carbon resistor can be calculated by the code given on it in the form of coloured strips.
Colour coding Colour Figure Black 0 Brown 1 Red 2 Orange 3 Yellow 4 Green 5 Blue 6 Violet 7 Grey 8 White 9
Tolerance power
Colour Tolerance Gold 5 % Silver 10 % No colour 20 %
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