Chapter: physics 11th 12th standard school college definition answer assignment examination viva question
Carbon resistors and Colour code for carbon resistors
Carbon resistors
The wire wound resistors are
expensive and huge in size. Hence, carbon resistors are used. Carbon resistor
consists of a ceramic core, on which a thin layer of crystalline carbon is
deposited. These resistors are cheaper, stable and small in size. The resistance
of a carbon resistor is indicated by the colour code drawn on it (Table 2.2). A
three colour code carbon resistor is discussed here. The silver or gold ring at
one end corresponds to the tolerance. It is a tolerable range ( -/+ ) of the
resistance. The tolerance of silver, gold, red and brown rings is 10%, 5%, 2%
and 1% respectively. If there is no coloured ring at this end, the tolerance is
20%. The first two rings at the other end of tolerance ring are significant
figures of resistance in ohm. The third ring indicates the powers of 10 to be
multiplied or number of zeroes following the significant figure.
Example :
The first yellow ring in Fig 2.4
corresponds to 4. The next violet ring corresponds to 7. The third orange ring
corresponds to 103. The silver ring represents 10% tolerance. The
total resistance is 47 Ã- 103 (-/+) 10% i.e. 47 k Ω, 10%. Fig 2.5
shows 1 k Ω, 5% carbon resistor.
Presently four colour code carbon resistors
are also used. For certain critical applications 1% and 2% tolerance resistors
are used.
Related Topics