Those elements
whose V-I curves are not straight lines are called non-linear elements because
their resistances are nor-linear resistances. Their V-I characteristics can be
represented by an equation of the form I=kVn + b.
whose V-I curves are not straight lines are called non-linear elements because
their resistances are nor-linear resistances. Their V-I characteristics can be
represented by an equation of the form I=kVn + b.
Where n is usually
not equal to one and the constant b may or may not be equal to zero.
not equal to one and the constant b may or may not be equal to zero.
Example of
non-linear elements are filament of incandescent lamps, diodes, themistors and
varistors. A varistor is a special resistor is a special resistor made of
carborundum crystal held together by a binder. Figure 1 below shows how current
through a varistor increase rapidly when applied voltage increases beyond a
certain amount (nearly 100V in the present case).
non-linear elements are filament of incandescent lamps, diodes, themistors and
varistors. A varistor is a special resistor is a special resistor made of
carborundum crystal held together by a binder. Figure 1 below shows how current
through a varistor increase rapidly when applied voltage increases beyond a
certain amount (nearly 100V in the present case).
There is a
corresponding rapid decrease in resistance when the current increases. Hence
varistors are generally used to provide over-voltage protection in certain circuits.
corresponding rapid decrease in resistance when the current increases. Hence
varistors are generally used to provide over-voltage protection in certain circuits.
A thermistor is made
of metallic oxide in a suitable binder and has a large negative coefficient of
resistance i.e. its resistance increases with increase in temperature as shown
in figure 2 below.
of metallic oxide in a suitable binder and has a large negative coefficient of
resistance i.e. its resistance increases with increase in temperature as shown
in figure 2 below.
Figure 3 below
shows how the resistance of an incandescent lamp increases with voltage.
shows how the resistance of an incandescent lamp increases with voltage.
Figure 4 below shows the V-I characteristics of a
typical silicon diode. For germanium diode, current is related to its voltage
by the relation
typical silicon diode. For germanium diode, current is related to its voltage
by the relation
