2. WIREWOUND POTENTIOMETER
• As shown, it consists of a
resistive wire wound on
insulating material.
• In this, the value of resistance of
a resistor depends on diameter,
length and cross section of a
wire and type of wire used.
• The whole assembly is enclosed
in a metal case.
3. USES OF POTENTIOMETER
1. In amplifier for volume control.
2. In TV sets for controlling volume, balance, linearity and brightness.
3. In various types of meters.
4. RESISTOR COLOR CODE
• It is used for finding out the value of resistance of a resistor.
• On the outer surface of resistor, a ring of different colors are marked as
shown.
• COLOR CODE CHARACTER:
• Black – 0, Brown – 1, Red – 2,
Orange – 3, Yellow – 4, Green –
5, Blue – 6, Violet – 7, Gray – 8,
White – 9, Gold – 10-1 , Silver –
10-2
5. • Now, to find out value of resistance, the rings are read from left end.
• The value of first two rings are written one after the other and put number
of zeros corresponding to the value of third ring.
• The fourth ring gives the tolerance. E.g. Gold ± 5 %, Silver ± 10 %, No color
or white ± 20 %.
• E.g. The first ring is yellow – 4, second ring is violet – 7, third ring is orange
– 3, fourth ring is silver - ±10 %, then the value of resistance of above color
code band resistor is = 47000 Ω = 47 K Ω ± 10 %.
6. POWER RATING OF RESISTOR
• It indicates the maximum wattage it can dissipate without excessive heat.
• It gives the indication of maximum current a resistor can safely carry.
• The physical size of resistor indicates its wattage.
• Greater the physical size, higher will be the power rating.
• TOLERANCE:
• The amount by which the actual resistance can be different from the color
code value.
• It is given in %.
• E.g. 1000 Ω resistor with ± 10 % tolerance can have resistance value
between 1100 Ω to 900 Ω.
• Smaller the tolerance, more accurate the resistance value and higher the
cost.
