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प्रश्न
Why is potentiometer preferred over a voltmeter for comparison of emf. of cells?
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उत्तर
Potentiometer is preferred over a voltmeter for comparison of emf of cells because of the following reasons:
(a) A potentiometer can measure the internal resistance of the cell, which a voltmeter cannot measure.
(b) A potentiometer can accurately measure small potential differences, which a voltmeter cannot.
(c) The accuracy of a potentiometer can also be increased by increasing the length of the wire, whereas the accuracy of the voltmeter is fixed.
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संबंधित प्रश्न
In the following potentiometer circuit, AB is a uniform wire of length 1 m and resistance 10 Ω. Calculate the potential gradient along the wire and balance length AO (= l).
Identify the correct options.
(a) An ammeter should have small resistance.
(b) An ammeter should have large resistance.
(c) A voltmeter should have small resistance.
(d) A voltmeter should have large resistance.
The current in a conductor and the potential difference across its ends are measured by an ammeter and a voltmeter. The meters draw negligible currents. The ammeter is accurate but the voltmeter has a zero error (that is, it does not read zero when no potential difference is applied). Calculate the zero error if the readings for two different conditions are 1.75 A, 14.4 V and 2.75 A, 22.4 V.
A voltmeter of resistance 400 Ω is used to measure the potential difference across the 100 Ω resistor in the circuit shown in the figure. (a) What will be the reading of the voltmeter? (b) What was the potential difference across 100 Ω before the voltmeter was connected?
A voltmeter consists of a 25 Ω coil connected in series with a 575 Ω resistor. The coil takes 10 mA for full-scale deflection. What maximum potential difference can be measured by this voltmeter?
A 6-volt battery of negligible internal resistance is connected across a uniform wire AB of length 100 cm. The positive terminal of another battery of emf 4 V and internal resistance 1 Ω is joined to the point A, as shown in the figure. Take the potential at B to be zero. (a) What are the potentials at the points A and C? (b) At which point D of the wire AB, the potential is equal to the potential at C? (c) If the points C and D are connected by a wire, what will be the current through it? (d) If the 4 V battery is replaced by a 7.5 V battery, what would be the answers of parts (a) and (b)?
If a constant potential difference is applied across a bulb, the current slightly decreases as time passes and then becomes constant. Explain.
A potential difference of 220 V is maintained across 12000 Ω rheostat. Then voltmeter V has a resistance of 6000 Ω and point C is at one fourth the distance from a to b. Then the reading of voltmeter is ______.
