electrical current in an electronic circuit. Resistors can also be used to
provide a specific voltage for an active device such as a transistor.
All other factors being equal, in a direct-current (DC) circuit, the current
through a resistor is inversely proportional to its resistance
Learn More
CIO Midmarket Resources
, and directly proportional to the voltage across it. This is the well-known
Ohm's Law. In alternating-current (AC) circuits, this rule also applies as long
as the resistor does not contain inductance or capacitance.
Resistors can be fabricated in a variety of ways. The most common type in
electronic devices and systems is the carbon-composition resistor. Fine
granulated carbon (graphite) is mixed with clay and hardened. The
resistance depends on the proportion of carbon to clay; the higher this
ratio, the lower the resistance.
Another type of resistor is made from winding Nichrome or similar wire on an
insulating form. This component, called a wirewound resistor, is able to
handle higher currents than a carbon-composition resistor of the same
physical size. However, because the wire is wound into a coil, the
component acts as an inductors as well as exhibiting resistance. This does
not affect performance in DC circuits, but can have an adverse effect in AC
circuits because inductance renders the device sensitive to changes in
frequency.
