Rheostat vs Potentiometer

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.
..................................................................................

That was Rheostat.
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.

Summary:

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.

To get to know more about rheostats:

Click here to go to mentioned Link

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THE WAR..!!

WAR..!!

DC power developed by Edison.
AC Power developed by Tesla.

We always get a doubt "Why this world is so crazy in AC power distribution while most of the equipment we use need DC power?"

Most of the devices work on DC power.Then why AC power whose characteristics are much complex to understand?

Generally the devices like mobile phones or many other gadgets need +5 volts or +12 volts for proper functioning.Then we think it would be nice if there were only +5 or +12 volt main supply at our plug in points rather than present 230V (AC,50Hz in India). Then we think, "What the hell is this AC power for?".

Reasons for not adopting DC power:

1)(Let us assume)For example a bulb needs 100V DC to work properly and a mobile phone requires +5 volts and other device needs +12 volts for functioning then there is a need of different DC voltage plug-in points. That indirectly means there should be respective distribution lines for each different voltage requirement. This is not economical way of providing electrical power as it is a costly process frankly speaking impractical method.

2)In worst case let us assume that the above mentioned method of providing different DC is practical then we need to question till how much distance it could be efficiently transmitted? in any power distribution electric losses are the main criteria to be focused up on..!!

the answer would:
For low voltage distribution, the distance up to which it could be distributed efficiently would be up to a maximum of 2 Kms. Anything more than that distance would account most of its share to electric losses rather than useful power. That implies for each and every colony there should be a separate electric power generation unit as such. Don't you think this method is too costly? While it comes to that of rural areas it would account most of the money in developing such power generation plants. So this method is ruled out.

3)another alternative which would be thought of is that it would be nice if higher DC voltage is distributed from power plant so that that after traveling long distance even though after attenuation the required signal can be made use of at the customer end.it indirectly means we are unnecessarily wasting much of generated power.

Higher voltages could not so easily be used with the DC system because there was no efficient low-cost technology that would allow reduction of a high transmission voltage to a low utilization voltage.

And we also know that AC can be converted into required DC voltage using a transformer and a rectifier circuit.
these all reasons were responsible in ruling out the DC power distribution lines
which were a little bit popular.


Any problem will definitely have a solution for sure..!!

The solution that came up wasThe solution that came up was use of AC power developed by Tesla.
The theory of AC power was in the initial stages and was greatly opposed by EDISON at that time. Edison developed the theory of DC distribution. where as Tesla developed the now popular AC distribution. These two great people developed their theories and were fighting for a dominant hand over one another.
This situation can be compared to that of a WAR, and so during that time this WAR was very famously known as

THE WAR OF CURRENTS

This is all about how the factors that demanded for a war like thing to happen.

To know more..

CLICK HERE TO KNOW THE DETAILED INFORMATION ABOUT WAR OF CURRENTS

AC had one major advantage over DC, and that was the distance it would travel along power lines, 100s of miles, where as DC could only travel a few miles. At the time DC was the only current that would power the current electric motors, this however would change upon Tesla’s work with rotary magnetic fields. Edison publicly campaigned against AC and Tesla, stating that AC was dangerous, and demonstrated killing various animals using the current.This is briefly about the war of currents.

By the 1900 Edison had lost the ‘war of the currents’ to AC and Tesla.

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