Resistors
A resistor entails the following two main characteristics :
(i) Its resistance (R) in ohms. …… The resistors are available from a fraction of an ohm to
many mega ohms.
(ii) The wattage rating. …… The power rating may be as high as several hundred watts or as
low as 1/10 watt.
Power rating indicates the maximum wattage the resistor can dissipate without
excessive heat (Too much heat can make the resistor burn open).
Classification of resistors
Read Also : Types of Resistors
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The resistors are classified as follows :
Fixed resistors.
The fixed resistor is the simplest type of resistor.
Fixed means that the unit is so constructed that its resistance value is constant and unchangeable.
These are made of a carbon composition and have a cover of black or brown hard plastics.
Tapped resistors
A tapped resistor is a resistor which has a tap, or connection, somewhere
along the resistance material. These resistors are usually wire wound type. If they have more than
one tap, they will have a separate terminal for each.
Variable resistors
A variable resistor has a movable contact that is used to adjust or select
the resistance value between two or more terminals. A variable resistor is commonly called a control.
Special resistors
The most common type of special resistors is the fusible type. A fusible
resistor have a definite resistance value and it protects the circuit much like a fuse.
Another special resistor is the temperature-compensating unit. Such resistors are used to provide special control of circuit that must be extremely stable in their operation.
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Schematic symbols for various resistors
Schematic symbols for various resistors are shown in Fig
Resistors used in electrical circuit
The following types of resistors are used in electrical circuits :
(i) Carbon resistors.
(ii) Wire-wound resistors on ceramic or plastic forms (as in case of rheostats etc.)
(iii) Deposited carbon resistors on ceramic base.
(iv) Deposited metal resistors on ceramic base.
(v) Printed, painted or etched circuit resistors.
Read Also :
Resistance|Unit of Resistance|Conductance
Ohms’s law solved Problems|Problems based on ohm’s law
What is Ohm’s Law? Ohm’s Law Statement Formula Examples
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