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%
From NCERT
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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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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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The circuit shown here is used to compare the e.m.f. of two cells E1 and E2(E1>E2). The null point is at C when the galvanometer is connected to E1. When the galvanometer is connected to E2, the null point will be 

(1) To the left of C

(2) To the right of C

(3) At C itself

(4) Nowhere on AB

Subtopic:  Meter Bridge & Potentiometer |
 73%
From NCERT
PMT - 1995
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In the Wheatstone's bridge (shown in the figure below) \(X=Y\) and \(A>B\). The direction of the current between \(a\) and \(b\) will be:

     

1. from \(a\) to \(b\).
2. from \(b\) to \(a\).
3. from \(b\) to \(a\) through \(c\).
4. from \(a\) to \(b\) through \(c\).
Subtopic:  Wheatstone Bridge |
 61%
From NCERT
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A resistance of 4 Ω and a wire of length 5 metres and resistance 5 Ω are joined in series and connected to a cell of e.m.f. 10 V and internal resistance 1 Ω. A parallel combination of two identical cells is balanced across 300 cm of the wire. The e.m.f. E of each cell is:

1. 1.5 V

2. 3.0 V

3. 0.67 V

4. 1.33 V

Subtopic:  Meter Bridge & Potentiometer |
 68%
From NCERT
PMT - 1997
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Constantan wire is used in making standard resistances because of its :

(1) Specific resistance is low

(2) Density is high

(3) Temperature coefficient of resistance is negligible

(4) Melting point is high

Subtopic:  Derivation of Ohm's Law |
 71%
From NCERT
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A potentiometer consists of a wire of length 4 m and resistance 10 Ω. It is connected to a cell of e.m.f. 2 V. The potential difference per unit length of the wire will be :

(1) 0.5 V/m

(2) 2 V/m

(3) 5 V/m

(4) 10 V/m

Subtopic:  Meter Bridge & Potentiometer |
 83%
From NCERT
PMT - 1999
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In the circuit shown PR, the reading of the galvanometer is same with switch S open or closed. Then 

(1) IR=IG

(2) IP=IG

(3) IQ=IG

(4) IQ=IR

Subtopic:  Wheatstone Bridge |
 64%
From NCERT
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