Current Electricity PYQs Set 8 (PDF)

Set 8 of 21 · Questions 211-240 of 612

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Mere Teacher · Previous Year Questions NEET Physics · Current Electricity · Set 8 (Q211-240)
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211. $Mobility of free electrons in a conductor is$ (1) $directly proportional to electron density$ (2) $directly proportional to relaxation time$ (3) $inversely proportional to electron density$ (4) $inversely proportional to relaxation time.$ 212. $A battery of e.m.f 10 V and internal resistance 0.5 Ω is connected across a variable resistance R . The value of R for which the power delivered in it is maximum is given by$ (1) $0.5 Ω$ (2) $1.0 Ω$ (3) $2.0 Ω$ (4) $0.25$ 213. $In a meter bridge experiment the ratio of the left gap resistance to the right gap resistance is 2 : 3 . The balance length from left end is$ (1) $20 cm$ (2) $60 cm$ (3) $50 cm$ (4) $40 cm$ 214. $An electron takes 40 \times 10^{3} s to drift from one end of a metal wire of length 2 m to its other end. The area of cross-section of the wire is 4 mm^{2} and it is carrying a current of 1.6 A . The number density of free electrons in the metal wire is$ (1) $8 \times 10^{28} m^{- 3}$ (2) $6 \times 10^{28} m^{- 3}$ (3) $4 \times 10^{28} m^{- 3}$ (4) $5 \times 10^{28} m^{- 3}$ 215. $A wire of resistance R is connected across a cell of emf ϵ and internal resistance r. The current through the circuit is I. In time t, the work done by the battery to establish the current I is$ (1) $ϵ It$ (2) $\frac{ϵ ^{2} t}{R}$ (3) $IRt$ (4) $I^{2} Rt$ 216. $A 2 W carbon resistor is color coded with green, black, red and brown respectively. The maximum current which can be passed through this resistor is$ (1) $20 mA$ (2) $100 mA$ (3) $0.4 mA$ (4) $63 mA$ 217. $An electric bulb is rated 60 W, 220 V The resistance of its filament is$ (1) $870 Ω$ (2) $780 Ω$ (3) $708 Ω$ (4) $807 Ω .$ 218. $In a building there are 15 bulbs of 45 W, 15 bulbs of 100 W, 15 small fans of 10 W and 2 heaters of 1 kW . The voltage of electric main is 220 V . The minimum fuse capacity (rated value) of building will be:$ (1) $5 A$ (2) $20 A$ (3) $25 A$ (4) $15 A$ 219. $A car has a fresh storage battery of emf. 12 V and internal resistance 2 \times 10^{- 2} Ω . If the starter motor draws a current of 80 A . Then the terminal voltage when the starter is on is$ (1) $10.4 V$ (2) $9.3 V$ (3) $12 V$ (4) $8.4 V$ 220. $Copper and silicon is cooled from 300 K to 60 K, the specific resistance$ (1) $decrease in copper but increase in silicon$ (2) $increase in copper but decrease in silicon$ (3) $increase in both$ (4) $decrease in both$ 221. $Two resistors R_{1} = (4 \pm 0.8) Ω and R_{2} = (4 \pm 0.4) Ω are connected in parallel. The equivalent resistance of their parallel combination will be:$ (1) $(4 \pm 0.4) Ω$ (2) $(2 \pm 0.4) Ω$ (3) $(2 \pm 0.3) Ω$ (4) $(4 \pm 0.3) Ω$ 222. $An aluminium wire is stretched to make its length 0.4% larger. Then percentage change in resistance is:$ (1) $0.4%$ (2) $0.2%$ (3) $0.8 %$ (4) $0.6 %$ 223. $A 6 volt battery is connected to the terminals of a three meter long wire of uniform thickness and resistance of 100 ohm. The difference of potential between two points on the wire separated by a distance of 50 cm will be$ (1) $2 volt$ (2) $3 volt$ (3) $1 volt$ (4) $1.5 volt$ 224. $There are ' n ' number of identical electric bulbs, each is designed to draw a power p independently from the mains supply. They are now joined in series across the mains supply. The total power drawn by the combination is:$ (1) $np$ (2) $p$ (3) $\frac{p}{n ^{2}}$ (4) $\frac{p}{n}$ 225. $n equal resistors are first connected in series and then connected in parallel. What is the ratio of the maximum to the minimum resistance?$ (1) $n$ (2) $1/ n^{2}$ (3) $n^{2}$ (4) $1/ n$ 226. $A galvanometer is used in laboratory for detecting the null point in electrical experiments. If, on passing a current of 6 mA it produces a deflection of 2^{\circ} its figure of merit is close to$ (1) $6 \times 10^{- 3} A / div$ (2) $666^{\circ} A / div .$ (3) $3 \times 10^{- 3} A / div$ (4) $333^{\circ} A / div$ 227. $Space between two concentric conducting spheres of radii a and b (b > a) is filled with a medium of resistivity ρ. The resistance between the two spheres will be:$ (1) $\frac{ρ}{4 π} (\frac{1}{a} - \frac{1}{b})$ (2) $\frac{ρ}{2 π} (\frac{1}{a} - \frac{1}{b})$ (3) $\frac{ρ}{2 π} (\frac{1}{a} + \frac{1}{b})$ (4) $\frac{ρ}{4 π} (\frac{1}{a} + \frac{1}{b})$ 228. $An electric bulb is rated 220 volt - 100 watt. The power consumed by it when operated on 110 volt will be$ (1) $25 watt$ (2) $50 watt$ (3) $75 watt$ (4) $40 watt$ 229. $In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across 52cm of the potentiometer wire. If the cell is shunted by resistance of 5 Ω, a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell$ (1) $2$ (2) $2.5$ (3) $1$ (4) $1.5$ 230. $An electric kettle takes 4 A current at 220 V How much time will it take to boil 1 kg of water from temperature 2 0^{o} C ? The temperature of boiling water is 10 0^{o} C .$ (1) $12.6 min$ (2) $4.2 min$ (3) $6.3 min$ (4) $8.4 min$ 231. $A piece of copper and a piece of germanium are cooled from room temperature to 80 K, Then, which one of the following is correct?$ (1) $Resistance of each will increase$ (2) $Resistance of each will decrease$ (3) $Resistance of copper will decrease while that of germanium will increase$ (4) $Resistance of copper will increase while that of germanium will decrease$ 232. $The resistance of a carbon resistor is 4.7 kΩ \pm 5 % . The colour of the third band is$ (1) $gold$ (2) $red$ (3) $violet$ (4) $orange$ 233. $A galvanometer having a coil of resistance 30Ω need 20 mA of current for full-scale deflection. If a maximum current of 3 A is to be measured using this galvanometer, the resistance of the shunt to be added to the galvanometer should be \frac{30}{X} Ω, where X is Options$ (1) $596$ (2) $149$ (3) $298$ (4) $447$ 234. $Wheatstone bridge principle is used to measure the specific resistance (S_{1}) of given wire, having length L, radius r. If X is the resistance of wire, then specific resistance is : S_{1} = X (\frac{π r ^{2}}{L}) .If the length of the wire gets doubled then the value of specific resistance will be :$ (1) $\frac{S _{1}}{4}$ (2) $2 S_{1}$ (3) $\frac{S _{1}}{2}$ (4) $S_{1}$ 235. $A battery with a 12 V emf has an initial charge of 80 A.h. If the potential across the terminals stays constant until battery is completely discharged, then this battery can deliver energy at the rate of 120 W for a time$ (1) $16 h$ (2) $8 h$ (3) $4 h$ (4) $5 h$ 236. $The resistance of a device component decreases as the current through it increases and it is described by the relation, R = \frac{0.2 I}{I - 4}, where I is the current. Determine the minimum power deliver. (Assume, I > 4)$ (1) $22.4 W$ (2) $18.6 W$ (3) $19.8 W$ (4) $21.6 W$ 237. $Charge passing through a conductor of cross-section 0.3 m^{2} is given by q = (3 t^{2} + 5 t + 2) C where ' t' is in seconds. The drift velocity at t = 2 s is (Concentration of electrons in the conductor = 2 \times 10^{25} (m^{- 3})$ (1) $0.77 \times 10^{- 5} ms^{- 1}$ (2) $0.93 \times 10^{- 5} ms^{- 1}$ (3) $1.77 \times 10^{- 5} ms^{- 1}$ (4) $2.08 \times 10^{- 5} ms^{- 1}$ 238. $Three unequal resistances are connected in parallel. Two of these resistances are in the ratio . The equivalent resistance of these three resistors connected in parallel is . What is the highest resistance value among these three resistances if no resistance is fractional?$ (1) $10Ω$ (2) $8Ω$ (3) $15Ω$ (4) $6Ω$ 239. $The resistance of a wire at 300 K is found to be 0.3Ω . If the temperature co-efficent of resistance of wire is 1.5 \times 10^{- 3} K^{- 1}, the temperature at which the resistance becomes 0.6Ω is$ (1) $720 K$ (2) $345 K$ (3) $993 K$ (4) $690 K .$ 240. $The accurate measurement of emf can be obtained using$ (1) $multimeter$ (2) $voltmeter$ (3) $voltameter$ (4) $potentiometer.$