rheostats and potentiometers?

Question

i am really confused with the two,,
ok in a potentiometer does the current always stay the same while we can vary the voltage,,

and dont they both do the same thing,, i mean you can reduce the resistance in a rheostat in series and hence get a greater voltage across the component,, isnt this the same thing as a potentiometer,,!!!
well we connect the potentiometer in parallel to get a specific voltage right,, so why to we regard them as two totally different things!!

by the way i have my A/l level physics practical test tommorrow,, so help is much appriciated

i am totally confused with the two can someone explain clearly what i need to know,,,

thanks alot!!!

Answer 1

I'll try and answer this like an electrical engineer.

Both devices are what are known as "variable resistors", meaning they are ajustable. That is why both have a knob of some sort, although many work like slide switches. The only difference is the power rating. Rheostats are not too common anymore, but once they were used to control primitive electric motors by increasing the resistance. The motor slowed, but the rheostat heated up. Rheostats were very durable and were constructed of metal wire wound around a ceramic core. The slider effectivly increased or decreased the length of wire the current had to cross. The wire had a fixed resistance and the more wire the current had to travel, the greater the resistance. Potentiometers (or "pots") are much smaller devices which handle far less current. The most common types have a thin strip of carbon film which replaces the coil of wire found in a rheostat. Potentiometers are usually only capable of handling half a watt in terms of power, whereas rheostats can handle hundreds of watts. Stereo volume controls are just potentiometers with extra fancy knobs. The volume control is "controlling" a network of power transistors and works like the knob on a faucet. Just a few ounces of pressure on the faucet knob controls 60 pounds of water pressure. The stereo power transistors are doing all the real work driving 200 watt speakers but need only need a fraction of a watt as far as control is concerned. This is why transistors are so important and also explains why there is so much heat sink material inside a stereo. In a sence, stereo power transistors are doing the job old fashioned rheostats used to do. Reguarding the rheostats themselves, they have been largely replaced by special heavy duty transistors known as SCR's. Silicon controlled rectifiers are basically how light dimmers work, but these devices can also control heating elements if the rectifier is correctly matched to the power characteristics of the heater. The controls on an electric stove are probably SCR's. Some electric motors can be controlled by SCR's but not all of them. Motor design has changed and modern electric motors are far more efficient because they use magnetic fields in an almost mechanical fashion. In these types of motors, decreasing the current simply stops the motor instead of slowing it down. Modern AC motor control involves changing the frequency of the current and this requires a multi stage circuit which turns high voltage AC to low voltage DC, generates a variable frequency DC current and then ramps the voltage back up. In this case it is neither resistance nor even the current which is affecting the motor, but subtle variations in the frequency of the AC current. The control is neither rheostat nor transistor, but a computer chip which generates variable frequencies. Power transistors then amplify this signal into useable current.

To conclude, don't think of electricity in terms of voltage - it is the current which is doing all the work. To decrease the current one can increase the resistance, either mechanically with a rheostat, or electronically with a potentiometer and transistor. Most modern electric motors have gotten so sophisticated they require computer chips if one wants to control their speed.

Hope this helps

Answer 2

Potentiometer Vs Rheostat

Answer 3

Rheostat Vs Potentiometer

Answer 4

A potentiometer has three terminals. A rheostat (which is an ancient name for a variable resistor that can handle a fair bit of current) only needs two terminals.

The point is that with a potentiometer, you can vary the applied voltage from the supply voltage all the way down to zero. You can't do that with a rheostat. You can vary the voltage applied to the component from the supply voltage down to some value determined by the ratio of the component's resistance to the maximum resistance of the rheostat.

The current through a potentiometer does not stay the same. The current that you are putting through the component has to come from somewhere!

Best wishes for your test.

Answer 5

The words potentiometer and rheostat refer to 2 different functions.
A potentiometer implies a potential divider designed to produce a varying voltage.
A rheostat is a variable resistance connected in series to vary current.

A rheostat is simply a variable resistance used to control power to a load and you are correct about the wiring. Only the slider and one other terminal are used.

A potentiometer uses all three terminals, enabling a variable voltage or signal to be tapped off from the slider.The correct term for the common terminal of a potentiometer is the slider.
Potentiometers and rheostats are made the same way, but rheostats are usually much "beefier", as they are generally used in high-power situations.
The slider is often connected to one or other terminal for safety reasons, in case it loses contact with the track.

https://www.electrikals.com/

Answer 6

This Site Might Help You.

RE:
rheostats and potentiometers?
i am really confused with the two,,
ok in a potentiometer does the current always stay the same while we can vary the voltage,,

and dont they both do the same thing,, i mean you can reduce the resistance in a rheostat in series and hence get a greater voltage across the component,, isnt this...

Answer 7

Rheostats, potentiometers, variable resistors, they all do the same thing, change resistance when the knob or shaft is turned. It is words. You have a car, an automobile or wheels, all mean the same thing. You will find, in electronic terminology that condenser and capacitor are the same thing also. It's a device that stores electric charge which is also called a voltage. Don't panic, you're young and things become clearer as you get older and learn more.

Answer 8

Potentiometers and rheostats work similar. Only difference is rheostats are designed to handle much higher voltage and current.

Answer 9

They both do about the same and I think the rheostat is like an old automotive hand down. Caution is always use a fuse resistor in series to protect the wattage problem is like this . If it is rated for 5 watts and u short half of it out u also reduced the wattage capability also.