What is potentio-meter? How is it used to compare the EMF of two Cell?
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A potentiometer is a device used to compare the e.m.f of any two cells, to measure the internal resistance of a cell and also to measure the potential difference across a resistor in a circuit.
We generally use a voltmeter to measure the potential difference across a resistor in a circuit.
When the voltmeter is connected across a resistor in a circuit, it draws a part of the current in the circuit, altering the overall potential difference that is to be measured across the given resistor. This alteration leads to an error in the measured value of the potential difference across the given resistor.
Thus, the voltmeter is not an ideal device to measure potential difference. An ideal voltmeter should have an infinite resistance.
As it is not practically possible to have an ideal voltmeter, we prefer to use another device called the stretched-wire potentiometer to voltmeter, which measures the potential difference across a resistor without drawing any current from the given circuit. We refer to the stretched-wire potentiometer as a potentiometer in our context.
A potentiometer consists of a long wire of about 10 metre in length, with a uniform cross-sectional area fixed to a wooden board. This is usually done with separate pieces of wire, of 1 metre each, , fixed parallel to each other to the board, with end points connected by copper strips so that the combination acts as a single stretched wire.
The end points of the wire, say A and B, are connected to a primary circuit consisting of a battery, B, a plug key, K, and a rheostat, Rh.
Here is the circuit diagram of the circuit we have just described.
The end, A, of the potentiometer wire is connected to the positive terminal of the battery. The end, B, is connected to the rheostat.
When the key is pressed, let ‘i’ be the constant current in the potentiometer wire along A to B. Thus, the potential gradually decreases from A to B.
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We generally use a voltmeter to measure the potential difference across a resistor in a circuit.
When the voltmeter is connected across a resistor in a circuit, it draws a part of the current in the circuit, altering the overall potential difference that is to be measured across the given resistor. This alteration leads to an error in the measured value of the potential difference across the given resistor.
Thus, the voltmeter is not an ideal device to measure potential difference. An ideal voltmeter should have an infinite resistance.
As it is not practically possible to have an ideal voltmeter, we prefer to use another device called the stretched-wire potentiometer to voltmeter, which measures the potential difference across a resistor without drawing any current from the given circuit. We refer to the stretched-wire potentiometer as a potentiometer in our context.
A potentiometer consists of a long wire of about 10 metre in length, with a uniform cross-sectional area fixed to a wooden board. This is usually done with separate pieces of wire, of 1 metre each, , fixed parallel to each other to the board, with end points connected by copper strips so that the combination acts as a single stretched wire.
The end points of the wire, say A and B, are connected to a primary circuit consisting of a battery, B, a plug key, K, and a rheostat, Rh.
Here is the circuit diagram of the circuit we have just described.
The end, A, of the potentiometer wire is connected to the positive terminal of the battery. The end, B, is connected to the rheostat.
When the key is pressed, let ‘i’ be the constant current in the potentiometer wire along A to B. Thus, the potential gradually decreases from A to B.
Please mark as brainliest....
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