Resistors are used as adjusting or controlling elements for signals in mechanical, electronic, and electrical devices such as the volume of sound, intensity of light, and the temperature of heat.
There are two kinds of resistors:
Potentiometer which is also known as “pot,” a resistor with three terminals and a sliding contact with an adjustable voltage divider.
Rheostat which is a variable resistor with two terminals. There are two types of rheostats; the rotary which have a curved wire coiled to save space, and the slider or linear which have a straight coiled wire.
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Rheostats are made of several different materials, such as, metal ribbons, fluids, and carbon disks. It uses the principles of Ohm’s law which states that the current will decrease as resistance to it increases, and it will increase as resistance to it is decreased. They are not polarized so they can operate in reverse direction too.
Potentiometers, on the other hand, are made with a resistive element, usually graphite, which is formed into an arc and a sliding contact or wiper that travels over the arc. The wiper is connected to another sliding contact to another terminal. It can also be made from resistance wire, carbon particles, and cermet. There are many types of potentiometers, they are:
Coming to potentiometer it looks as shown on right side..
String which is a multi-turn potentiometer and used as a position transducer.
Linear Slider which has a sliding control instead of a dial control.
Linear Taper wherein the resistance between the contact and terminal is in proportion to the distance between them.
Logarithmic which has resistive elements that vary from one end to the other and is used in audio amplifiers.
Digital which has electronic components.
Membrane which uses a conductive membrane with a sliding element to contact a resistor voltage divider and are used to sense positions.
Potentiometers have low power and are most commonly used for audio devices to control television brightness, contrast, and color, and as position transducers in joysticks and other such mechanisms.
Rheostats are used in household appliances such as fans, mixers, power tools, and electric ovens. They are also used to control the motors of large industrial machines.
While rheostats and potentiometers are still used today, they are being replaced by the triac, also known as Silicon Controlled Rectifier (SCR) because their mechanical parts corrode and break after some time which can cause them to malfunction.
1.A potentiometer is a resistor with three terminals and a sliding contact with an adjustable voltage divider while a rheostat is a variable resistor with two terminals.
2.A potentiometer is made with a resistive element such as graphite, resistance wire, carbon particles, and cermet while a rheostat is made of several different materials such as metal ribbons, fluids, and carbon disks.
3.A potentiometer has low power and is used for audio devices, television control, and as a transducer while a rheostat is used for control of appliances like fans, mixers, and the motors of large industrial machines.
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