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191.

Three resistances 2 Ω, 3 Ω and 4 Ω are connected in parallel. The ratio of currents passing through them when a potential difference is applied across its ends will be

5 : 4 : 3

6 : 3 : 2

4 : 3 : 2

6 : 4 : 3

192.

Four identical cells of emf E and internal resistance r are to be connected in series. Suppose, if one of the cell is connected wrongly, the equivalent emf and effective internal resistance of the combination is

2E and 4r

4E and 4r

2E and 2r

4E and 2r

193.

In the circuit shown below, the ammeter and the voltmeter readings are 3A and 6V respectively. Then, the value of the resistance R is

< 2 Ω

2 Ω

≥ 2 Ω

> 2 Ω

194.

Two cells of emf E_{1} and E_{2} are joined in opposition (such that E_{1} > E_{2}). If r_{1} and r_{2} be the internal resistances and R be the external resistance, then the terminal potential difference is

$\frac{{\mathrm{E}}_{1}-{\mathrm{E}}_{2}}{{\mathrm{r}}_{1}+{\mathrm{r}}_{2}}\times \mathrm{R}$

$\frac{{\mathrm{E}}_{1}+{\mathrm{E}}_{2}}{{\mathrm{r}}_{1}+{\mathrm{r}}_{2}}\times \mathrm{R}$

$\frac{{\mathrm{E}}_{1}-{\mathrm{E}}_{2}}{{\mathrm{r}}_{1}+{\mathrm{r}}_{2}+\mathrm{R}}\times \mathrm{R}$

$\frac{{\mathrm{E}}_{1}+{\mathrm{E}}_{2}}{{\mathrm{r}}_{1}+{\mathrm{r}}_{2}+\mathrm{R}}\times \mathrm{R}$

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195.

The resistance ofa bulb filament is 100 Ω at a temperature of 100°C. If its temperature coefficient of resistance be 0.005 per°C, then its resistance will become 200 Ω at a temperature

500°C

300°C

200°C

400°C

196.

In Wheatstone network, P = 2 Ω, Q = 2 Ω, R = 2 Ω and S = 3 Ω. The resistance with which S is to be shunted in order that the bridge may be balanced is

4 Ω

1 Ω

6 Ω

2 Ω

197.

Two parallel wires 1 m apart carry currents of 1 A and 3 A respectively in opposite directions. The force per unit length acting between two wires is

6 × 10

^{-5}Nm^{-1}repulsive6 × 10

^{-7}Nm^{-1}repulsive6 × 10

^{-5}Nm^{-1}attractive6 × 10

^{-7}Nm^{-1}attractive

198.

Mobility of free electrons in a conductor is

directly proportional to electron density

directly proportional to relaxation time

inversely proportional to electron density

inversely proportional to relaxation time

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199.

Variation of resistance of the conductor with temperature is as shown

The temperature coefficient (α) of the conductor is

$\frac{{\mathrm{R}}_{0}}{\mathrm{m}}$

mR

_{0}m

^{2}R_{0}$\frac{\mathrm{m}}{{\mathrm{R}}_{0}}$

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