plz explain the working of a rheostat as well.
i cannot understand that when there is already a resistance from the load in a circuit, how r we changing this resistance. that cannot be decreased .can it
i am really very confused. plz explain.
[plz no foolery answers. i would prefer some seriousness. its not that i dont like sarcasm or jokes, but just now, i'm really not in a mood .]
2006-10-18 06:13:44 · 4 answers · asked by catty 4 in Science & Mathematics ➔ Engineering
As other people have noted, a rheostat is usually a device that has a contact wiper that moves up and down a length of resistive material. Since the total resistance of the material is equal to the resistivity time the effective length, making the contact move up and down either increases or decreases the effective length of the resistive material that the electrons have to flow through before they reach the wiper, and thus this increases the effective resistance of the variable resistor.
Why have a variable resistor? Remember Ohm's law? V = I * R? Or, put another way, I = V/R. Increase the resistance (R), then you decrease the current (I). Normally used as a volume control.
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Can also be used as a speed control on a motor (like your fan).
2006-10-18 07:28:45 · answer #1 · answered by Randy G 7 · 0⤊ 0⤋
You are correct that the resistance in a given length of wire cannot easily be changed without changing temperature.
However you can change resistance on a circuit by adding something like a rheostat.
The rheostat is a loop of wire with a contact point. You change the resistance of the rheostat by moving the contact point upper or lower on the loop (making less wire to travel).
Picture having a slinky with a wire on one end and a connector you can attach at any point. Connecting to the far end is lots of resistance (more slinky to move through), connecting farther down is less resistance.
2006-10-18 13:23:40 · answer #2 · answered by Javelinl 3 · 0⤊ 0⤋
A volume control on a stereo is a variable resistor. I think that as you turn the knob it varies the amount of carbon (resistance) that the circuit travels through.
2006-10-18 13:17:35 · answer #3 · answered by tumbleweed1954 6 · 0⤊ 0⤋
resistance is ; whats slows or decreases the amount of electrons flowing thru a conducting medium or substance (metal usually). it's measured in "ohm's" , or milliohms ,or megaohms. voltage is the force that pushes the electrons ;resistance trys to stop that flow. variable is ; being able to change the resistance
2006-10-18 13:29:39 · answer #4 · answered by pahump1@verizon.net 4 · 0⤊ 0⤋