A potentiometer is used for the comparison of e.m.f. of two cells E1 and E2. For cell E1 the no deflection point is obtained at 20cm and for E2 the no deflection point is obtained at 30cm. The ratio of their e.m.f.'s will be 

(1) 2/3

(2) 1/2

(3) 1

(4) 2

Subtopic:  Meter Bridge & Potentiometer |
 90%
From NCERT
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If the length of the potentiometer wire is increased, then the length of the previously obtained balance point will :

(1) Increase

(2) Decrease

(3) Remain unchanged

(4) Become two times

Subtopic:  Meter Bridge & Potentiometer |
 60%
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If in the experiment of Wheatstone's bridge, the positions of cells and galvanometer are interchanged, then balance points will

(1) Change

(2) Remain unchanged

(3) Depend on the internal resistance of cell and resistance of galvanometer

(4) None of these

Subtopic:  Wheatstone Bridge |
 78%
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Two cells when connected in series are balanced on 8m on a potentiometer. If the cells are connected with polarities of one of the cells  reversed, they balance on 2m. The ratio of e.m.f.'s of the two cells is

(1) 3 : 5

(2) 5 : 3

(3) 3 : 4

(4) 4 : 3

Subtopic:  Grouping of Cells |
 80%
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A voltmeter has a resistance of G ohms and range V volts. The value of resistance used in series to convert it into a voltmeter of range nV volts is :

(1) nG

(2) (n1)G

(3) Gn 

(4) G(n1)

Subtopic:  Conversion to Ammeter & Voltmeter |
 76%
From NCERT
PMT - 1999
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Which of the following statement is wrong:

(1) Voltmeter should have high resistance

(2) Ammeter should have low resistance

(3) Ammeter is placed in parallel across the conductor in a circuit

(4) Voltmeter is placed in parallel across the conductor in a circuit

Subtopic:  Conversion to Ammeter & Voltmeter |
 69%
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In the diagram shown, the reading of voltmeter is 20 V and that of ammeter is 4 A. The value of R should be (consider given ammeter and voltmeter are not ideal) :

(1) Equal to 5 Ω

(2) Greater from 5 Ω

(3) Less than 5 Ω

(4) Greater or less than 5 Ω depends on the material of R

Subtopic:  Derivation of Ohm's Law |
From NCERT
PMT - 1997
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A moving coil galvanometer has a resistance of 50 Ωand gives full scale deflection for 10 mA. How could it be converted into an ammeter with a full scale deflection for 1A :

(1) 50/99 Ω in series

(2) 50/99 Ω in parallel

(3) 0.01 Ω in series

(4) 0.01 Ω in parallel

Subtopic:  Conversion to Ammeter & Voltmeter |
 77%
From NCERT
PMT - 1996
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Which is a wrong statement :

(1) The Wheatstone bridge is most sensitive when all the four resistances are of the same order

(2) In a balanced Wheatstone bridge, interchanging the positions of galvanometer and cell affects the balance of the bridge

(3) Kirchhoff's first law (for currents meeting at a junction in an electric circuit) expresses the conservation of charge

(4) The rheostat can be used as a potential divider

Subtopic:  Wheatstone Bridge |
 84%
PMT - 1994
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\(AB\) is a wire of uniform resistance. The galvanometer \(G\) shows no current when the length \(AC= 20~\text{cm}\) and \(CB = 80~\text{cm}\). The resistance \(R\) is equal to: 


1. \(2~\Omega\)
2. \(8~\Omega\)
3. \(20~\Omega\)
4. \(40~\Omega\)

Subtopic:  Meter Bridge & Potentiometer |
 91%
From NCERT
PMT - 1995
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