Current Electricity PYQs Set 6 (PDF)

Set 6 of 25 · Questions 151-180 of 723

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Mere Teacher · Previous Year Questions JEE Main Physics · Current Electricity · Set 6 (Q151-180)
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151. $To determine the internal resistance of a cell by using a potentiometer the null point is at 1 m when the cell is shunted by 3Ω resistance and at a length 1.5 m . When cell is shunted by 6Ω resistance, the internal resistance of the cell is$ (1) $4Ω$ (2) $8Ω$ (3) $3Ω$ (4) $6Ω$ 152. $A current of 5 A is passing through a metallic wire of cross sectional area 4 \times 10^{- 6} m^{2} . If the density of charge carriers of the wire is 5 \times 10^{26} m^{- 3}, the drift velocity of the electrons will be$ (1) $1 \times 10^{2} m s^{- 1}$ (2) $1.56 \times 10^{- 2} m s^{- 1}$ (3) $1.56 \times 10^{- 3} m s^{- 1}$ (4) $1 \times 10^{- 2} m s^{- 1} .$ 153. $A 30 V, 90 W lamp is to be operated on a 120 V D.C. line. For proper glow, a resistor of ohm should be connected in series with the lamp.$ (1) $40$ (2) $10$ (3) $20$ (4) $30$ 154. $A car battery of emf 12 V and internal resistance 5 \times 1 0^{- 2} Ω, receives a current of 60 amp from external source, then terminal potential difference of battery is$ (1) $12 V$ (2) $9 V$ (3) $15 V$ (4) $20 V$ 155. $The charge flowing in a conductor changes with time as Q (t) = αt - β t^{2} + γ t^{3} . Where α, β and γ are constants. Minimum value of current is:$ (1) $α - \frac{3 β ^{2}}{γ}$ (2) $α - \frac{γ ^{2}}{β}$ (3) $β - \frac{α ^{2}}{3 γ}$ (4) $α - \frac{β ^{2}}{3 γ}$ 156. $The charge following through a resistance R varies with time t as Q = at - b t^{2}, where a and b are positive constants. The total heat produced in R is$ (1) $\frac{a ^{3} R}{3 b}$ (2) $\frac{a ^{3} R}{2 b}$ (3) $\frac{a ^{3} R}{b}$ (4) $\frac{a ^{3} R}{6 b}$ 157. $A moving coil galvanometer, having a resistance G, produces full scale deflection when a current I_{g} flows through it. This galvanometer can be converted into (i) an ammeter of range 0 to I_{0} (I_{0} > I_{g}) by connecting a shunt resistance R_{A} to it and (ii) into a voltmeter of range 0 to V (V = G I_{0}) by connecting a series resistance R_{v} to it. Then,$ (1) $R_{A} R_{V} = G^{2} (\frac{I _{0} - I _{g}}{I _{g}}) and \frac{R _{A}}{R _{V}} = (\frac{I _{g}}{I _{0} - I _{g}})^{2}$ (2) $R_{A} R_{V} = G^{2} and \frac{R _{A}}{R _{V}} = (\frac{I _{g}}{I _{0} - I _{g}})^{2}$ (3) $R_{A} R_{V} = G^{2} (\frac{I _{g}}{I _{0} - I _{g}}) and \frac{R _{A}}{R _{V}} = (\frac{I _{0} - I _{g}}{I _{g}})^{2}$ (4) $R_{A} R_{V} = G^{2} and \frac{R _{A}}{R _{V}} = \frac{I _{g}}{( I _{0} - I _{g} )}$ 158. $A uniform metal wire carries a current of 2 A when an ideal cell of 3.4 V is connected across it. The wire has mass 8.92 \times 10^{- 3} kg, density 8.92 \times 10^{3} kgm^{- 3} and resistivity 1.7 \times 10^{- 8} Ωm . Then the length of the wire is$ (1) $5 m$ (2) $6.8 m$ (3) $10 m$ (4) $15.6 m$ 159. $Two electric resistors have equal values of resistance R. Each can be operated with a power of 320 watts (W) at 220 volts. If the two resistors are connected in series to a 110 volts electric supply, then the power generated in each resistor is$ (1) $90 watts$ (2) $80 watts$ (3) $60 watts$ (4) $20 watts$ 160. $Drift speed of electrons, when 1.5 A of current flows in a copper wire of cross section 5 mm^{2}, is v. If the electron density in copper is 9 \times 10^{28} / m^{3} the value of v in mm / s close to (Take charge of electron to be = 1.6 \times 10^{- 19} C)$ (1) $0.02$ (2) $3$ (3) $2$ (4) $0.2$ 161. $A galvanometer of resistance 100Ω when connected in series with 400Ω measures a voltage of upto 10 V . The value of resistance required to convert the galvanometer into ammeter to read upto 10 A is x \times 10^{- 2} Ω . The value of x is:$ (1) $2$ (2) $800$ (3) $20$ (4) $200$ 162. $Two identical heater filaments are connected first in parallel and then in series. At the same applied voltage, the ratio of heat produced in same time for parallel to series will be:$ (1) $1 : 4$ (2) $4 : 1$ (3) $2 : 1$ (4) $1 : 2$ 163. $A charged particle having drift velocity of 7.5 \times 10^{- 4} ms^{- 1} in an electric field of 3 \times 10^{- 10} Vm^{- 1}, has a mobility (in m^{2} V^{- 1} s^{- 1}) of [NEET 2020]$ (1) $2.5 \times 10^{6}$ (2) $2.5 \times 10^{- 6}$ (3) $2.25 \times 10^{- 15}$ (4) $2.25 \times 10^{15}$ 164. $You are given several identical resistances each of value R = 10Ω and each capable of carrying a maximum current of one ampere. It is required to make a suitable combination of these resistances of 5 Ω which can carry a current of 4 ampere. The minimum number of resistances of the type R that will be required for this job is$ (1) $4$ (2) $10$ (3) $8$ (4) $20$ 165. $A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf ‘s is$ (1) $3 : 4$ (2) $3 : 2$ (3) $5 : 1$ (4) $5 : 4$ 166. $A cylindrical wire is stretched up to twice of its length, then its resistance becomes:$ (1) $4 times$ (2) $unchanged$ (3) $\frac{1}{2} times$ (4) $2 times$ 167. $In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in USA will be$ (1) $R$ (2) $2 R$ (3) $R /4$ (4) $R /2$ 168. $A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it$ (1) $increases, thermal velocity of the electron increases$ (2) $decreases, thermal velocity of the electron increases$ (3) $increases, thermal velocity of the electron decreases$ (4) $decreases, thermal velocity of the electron decreases.$ 169. $A battery consists of a variable number n of identical cells (having internal resistance r each) which are connected in series. The terminals of the battery are short-circuited and the current I is measured. Which of the graphs shows the correct relationship between I and n? [NEET 2018]$ (1) (2) (3) (4) 170. $A 5^{o} C rise in temperature is observed in a conductor by passing acurrent. When the current is doubled the rise in temperature will be approximately$ (1) $2 0^{o} C$ (2) $1 6^{o} C$ (3) $1 0^{o} C$ (4) $1 2^{o} C$ 171. $A galvanometer of resistance has 50 divisions on its scale and has sensitivity of 20 μA / division. It is to be converted to a voltmeter with three ranges, of 0 - 2 V, 0 - 10 V and 0 - 20 V . The appropriate circuit to do so is:$ (1) (2) (3) (4) 172. $A resistance of 20Ω is connected in the left gap of a metre bridge and an unknown resistance greater than 20Ω is connected in the right gap. When these resistances are interchanged, the balance point shifts by 20 cm . the unknown resistance is$ (1) $25Ω$ (2) $40Ω$ (3) $35Ω$ (4) $30Ω$ 173. $An electrical bulb rated 220 V, 100 W, is connected in series with another bulb rated 220 V, 60 W. If the voltage across combination is 220 V, the power consumed by the 100 W bulb will be about \dots. W.$ 174. $A cylindrical wire of radius 0.5 mm and conductivity 5 \times 10^{7} S/m is subjected to an electric field of 10m V/m. The expected value of current in the wire will be x³π mA. The value x of is:$ 175. $In a potentiometer arrangement, a cell gives a balancing point at 75 cm length of wire. This cell is now replaced by another cell of unknown emf. If the ratio of the emfs of two cells respectively is 3 : 2, the difference in the balancing length of the potentiometer wire in above two cases will be______cm.$ 176. $A cylindrical conductor of length 2 m and area of cross-section 0.2 mm^{2} carries an electric current of 1.6 A when its ends are connected to a 2 V battery. Mobility of electrons in the conductor is α \times 10^{- 3} m^{2} / V . s . The value of α is : (electron concentration = 5 \times 10^{28} / m^{3} and electron charge = 1.6 \times 10^{- 19} C)$ 177. $A 1m long copper wire carries a current of 1A. If the cross section of the wire is 2.0 m m^{2} and the resistivity of copper is 1.7 x 10^{- 8} Ω m. the force experienced by moving electron in the wire is ______ x 1 0^{- 23} N. (charge on electron = 1.6 x 1 0^{- 19} C)$ 178. $The length of a given cylindrical wire is increased to double of its original length. The percentage increase in the resistance of the wire will be ____%.$ 179. $A cell, shunted by a 8 Ω resistance, is balanced across a potentiometer wire of length 3m. The balancing length is 2 m when the cell is shunted by 4 Ω resistance. The value of internal resistance of the cell will be_____Ω .$ 180. $If a copper wire is stretched to increase its length by 20%. The percentage increase in resistance of the wire is ______%.$