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diff between Rheostat and Potentiometer

justin07

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i wanted to know the difference between like a 25 ohm rheostat and a 25 ohm potentiometer
iam pretty sure a pot is like a resistor but iam a total electronic noob lol on the reviews it said it has the same function as a pot but i want to make sure before i buy it and use in it somthing
 

Hemlock_Mike

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A rehostat is a variable resistor with 2 legs. It controls current.
A potentiometer is a variable resistor with 3 legs. It controls voltage (potential) unless you use only two legs !! then it to is a rehostat !!!
Better sign up for Elec 101 at some school !!! This is the basics of electronics starting with ohms law. It will be difficult to understand what you are doing in your circuit without this knowledge and here is a great opportunity to learn.

Mike
 

Things

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basically they are the same thing. in a different package, and as mike said, the rheostat has 2 legs, and the potentiometer has 3. in the end, they are all just variable resistors
 

justin07

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Gazoo said:
True but a rheostat is known for handling more power.
it said something like 3 watts but basically it will do the same thing far as current and stuff?


o did see mike and things post thank you for the answers lol that about clears it up but the radio shack rheostat had 3 legs also i guess the middle is for grounds. well the reviews say it is lol and yea i do need electronics 101 lol
 

Hemlock_Mike

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Justin -

It depends on how you hook it up and for what purpose in the circuit. Actually, Rehostat is an old almost obsolete term.  Pots come in all ranges of resistance and power up to at least 100 watts.

V=IxR P=VxI =I*2xR There - Now you know.

Mike

The middle is for grounds ?? Coffee grounds ??? NNnnooooooo. That's usually the adjusted output.
 

justin07

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ah i meant ground lol thats just what some 1 said on the review
v= voltage
i=current
r=resistants
what does p mean? :-/
 

justin07

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i figured p = power but didnt want to look more stupid lol

another thing about ohms law is r=v/i so lets say 3v/.2(300ma)=10 ohms of resistants but thats assuming 1amp right? 3/(300/1000 = 3000/300 which is 10 ohms of resistants but lets say my battery has 1200 mah at 3v would it still be same as above or 3/(300/1200) = 3600(?(3.6v but 2 1.5v doesnt =3.6? lol)/300 = 12 ohms of resistants?
 

Things

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yes rheostats can handle a bit more power due to their size and simplicity. potentiometers use "rings" that have a higher resistance, so when a slider passes around the ring, the resistance decreases. rheostats use "coils" of wire, and the same "slider that goes over it.
so basically a rheostat is an old version of a potentiometer.
 

wilheldp

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justin07 said:
i figured p = power but didnt want to look more stupid lol

another thing about ohms law is r=v/i so lets say 3v/.2(300ma)=10 ohms of resistants but thats assuming 1amp right? 3/(300/1000 = 3000/300 which is 10 ohms of resistants but lets say my battery has 1200 mah at 3v would it still be same as above or 3/(300/1200) = 3600(?(3.6v but 2 1.5v doesnt =3.6? lol)/300 = 12 ohms of resistants?
First off, it's resistance. I'm not sure I understand you "assumption" of 1amp. The ratings on batteries are mAh, which is milliAmp hours. So, if you have a circuit drawing 300mA (which is 0.3A, I think you had a typo with that .2), then you will be able to run that circuit for 4 hours at 3V with a 1200mAh battery (300mA * 4 hours = 1200mAh). This is all theoretical, though, since you would have to discharge the battery 100% to get that much performance...and your current would have to remain constant thoughout the entire battery discharge.
 

justin07

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ah ok ty and it was a typo with the .2 i was thinking it the battery just put out 1200 ma at once i never considered the hour lol :-/ ty
 

wilheldp

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justin07 said:
ah ok ty and it was a typo with the .2 i was thinking it the battery just put out 1200 ma at once i never considered the hour lol  :-/  ty
You're welcome. I don't know much about lasers, so I try to "give back" to the forum on stuff I do know.
 

Xenodius

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Confusing-- I have a 3 legged, 25 ohm, 3 watt 'rheostat' from RS...

Works fine for driving the diode... :-?

(Goes down to .2 ohms)
 




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