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Principle of potentiometer?

explain on the level of 12 standard
Member since:
February 09, 2006
Total points:
91,563 (Level 7)

he original potentiometer is a type of bridge circuit for measuring voltages. The word itself derives from the phrase "voltage potential," and "potential" was used to refer to "strength." The original potentiometers are divided into four main classes: the constant resistance potentiometer, the constant current potentiometer, the microvolt potentiometer and the thermocouple potentiometer.
Constant current potentiometer

This is used for measuring voltages below 1.5 volts. In this circuit, the unknown voltage is connected across a section of resistance wire the ends of which are connected to a standard electrochemical cell that provides a constant current through the wire, The unknown emf, in series with a galvanometer, is then connected across a variable-length section of the resistance wire using a sliding contact(s). The sliding contact is moved until no current flows into or out of the standard cell, as indicated by a galvanometer in series with the unknown emf. The voltage across the selected section of wire is then equal to the unknown voltage. All that remains is to calculate the unknown voltage from the current and the fraction of the length of the resistance wire that was connected to the unknown emf. The galvanometer does not need to be calibrated, as its only function is to read zero. When the galvanometer reads zero, no current is drawn from the unknown electro motive force and so the reading is independent of the source's internal resistance

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thankyou,you have solved my problem to a gret extent.

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• Member since:
August 11, 2006
Total points:
4,173 (Level 4)
Are you referring to the resistance device that has a blade that swipes across a resistive material thereby creating variable resistance? As in the volume knob on older TV sets, portable radios and such?
• Member since:
June 21, 2006
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3,399 (Level 4)
The simplest form of potentiometer is a long piece of wire (say 1mtr long) with a connection at each end. A simple blade can be used to make contact at any point along the wire.

The wire has resistance. If we measure the length of the wire and the distance from one end at which we arrange for the blade to make contact, we are able to determine the ratio of the resistance of one section of the wire to the other. It is simply the ratio of the two lengths.

Using the potentiometer in a bridge circuit, we can set the contact such that the ration of resistance is the a same as the ratio between a known and unknown resistance.

We can use the potentiometer to measure voltages and resistances by comparing them with a standard using nothing but the ratio of two distances.
• Member since:
June 17, 2006
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4,153 (Level 4)
• Member since:
June 21, 2006
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it is based on the wheatstone principle. however, the wire is lonher then a metre bridge. use a potentiometer the compare the EMFs of daniel and leclanche cells.
• Member since:
July 26, 2006
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4,556 (Level 4)
Its a dimmer switch.
• Member since:
January 31, 2006
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1,366 (Level 3)
well its a relatively easy concept to understand
www.s-cool.co.uk will help u!
cheers!
• Member since:
April 17, 2006
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34,552 (Level 7)
A potentiometer is like taking an elevator.

There are some express elevators that only stop on the ground floor and say, the 50th floor. This is like a fixed resistor with a fixed value.

A potentiometer is not like that.

A potentiometer instead, allows you to stop at every floor between the ground and the 50th floor.

You can get down at any level you wish.

A potentiometer is a variable resistor, say for example, 100K ohms. There is a center tap that if you set it to the half way mark, will break the resistance to 50K+50K. The ability to do this allows us to use it as a voltage divider to control the speed of a fan, a light dimmer or the volume on your MP3 player for example.
• Member since:
August 05, 2006
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51,342 (Level 7)
I have no idea what the level of 12 standard is, but a potentiometer is basically a variable voltage divider. Think of it as 2 resistors connected in series with one of them increasing as the other one decreases and doing so in such a way that their total series resistance is a constant.

Doug
• by dwarf
Member since:
August 30, 2006
Total points:
1,804 (Level 3)
It's a principle of voltage division like the name itself. Potentiometer is useless if there is no potential difference applied on it.