Q. No.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
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
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
\(AB\) 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. \(40~\Omega\)
The circuit shown here is used to compare the e.m.f. of two cells and . 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
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 \(c\). |
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
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
The net resistance of a voltmeter should be large to ensure that :
| 1. | It does not get overheated |
| 2. | It draws excessive current |
| 3. | It can measure large potential difference |
| 4. | It does not appreciably change the potential difference to be measured |
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