Current Electricity PYQs Set 5 (PDF)

Set 5 of 21 · Questions 121-150 of 612

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Mere Teacher · Previous Year Questions NEET Physics · Current Electricity · Set 5 (Q121-150)
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121. $A resistor develops 500 J of thermal energy in 20 s when a current of 1.5 A is passed through it. If the currentis increased from 1.5 A to 3 A, what will be the energy developed in 20 s .$ (1) $1500 J$ (2) $1000 J$ (3) $500 J$ (4) $2000 J$ 122. $A carbon resistor of (47 \pm 4.7) kΩ is to be marked with rings of different colours for its identification. The colour code sequence will be$ (1) $Violet‐Yellow‐Orange‐Silver$ (2) $Yellow‐Violet‐Orange‐Silver$ (3) $Yellow‐Green‐Violet‐Gold$ (4) $Green‐Orange‐Violet‐Gold$ 123. $The masses of the wires of copper is in the ratio of 1 : 3 : 5 and their lengths are in the ratio of 5: 3: 1. The ratio of their electrical resistance is$ (1) $1 : 3 : 5$ (2) $5 : 3 : 1$ (3) $1: 25: 125$ (4) $125: 15: 1$ 124. $The resistance of a wire is R ohm. If it is melted and stretched to n times its original length, its new resistance will be [NEET 2017]$ (1) $nr$ (2) $\frac{R}{n}$ (3) $n^{2} R$ (4) $\frac{R}{n ^{2}}$ 125. $The resistance of the bulb filament is 100Ω at a temperature of 100^{\circ} C . If its temperature coefficient of resistance be 0.005 per^{\circ} C, its resistance will become 200Ω at a temperature$ (1) $400^{\circ} C$ (2) $200^{\circ} C$ (3) $300^{\circ} C$ (4) $500^{\circ} C$ 126. $In the potentiometer, when the cell in the secondary circuit is shunted with 4Ω resistance, the balance is obtained at the length 120 cm of wire. Now when the same cell is shunted with 12Ω resistance, the balance is shifted to a length of 180 cm. The internal resistance of cell is____Ω$ (1) $4$ (2) $12$ (3) $6$ (4) $3$ 127. $Assertion (A): When a wire of aluminium and another wire of silicon are heated from room temperature to 80^{\circ} C, then conductivity of aluminium increases and that of silicon decreases. Reason (R): Aluminium has positive temperature coefficient of resistivity and silicon has negative temperature coefficient of resistivity.$ (1) $Both (A) and (R) are correct and (R) is the correct explanation of (A) .$ (2) $Both (A) and (R) are correct but (R) is not the correct explanation of (A) .$ (3) $(A) is correct but (R) is not correct.$ (4) $(A) is not correct but (R) is correct.$ 128. $A galvanometer having a coil resistance 100Ω gives a full-scale deflection when a current of 1 mA is passed through it. What is the value of the resistance which can convert this galvanometer into a voltmeter giving full scale deflection for a potential difference of 10 V ?$ (1) $0.99 KΩ$ (2) $9.9 KΩ$ (3) $9.8 KΩ$ (4) $10 KΩ$ 129. $A 100 W tungsten light bulb has a resistance of 250Ω when it as turned ON and 25Ω when turned OFF. The ambient room temperature is 25^{\circ} C . Find the temperature of the filament when the bulb is turned ON. (Let α_{tungsten} = 4.5 \times 10^{- 3} /^{\circ} C)$ (1) $2600^{\circ} C$ (2) $2025^{\circ} C$ (3) $2500^{\circ} C$ (4) $2625^{\circ} C$ 130. $A current through a wire depends on time as i = α_{0} t + β t^{2} where α_{0} = 20 A/s and β = 8 A s^{- 2} . Find the charge crossed through a section of the wire in 15 s.$ (1) $2100C$ (2) $260C$ (3) $2250C$ (4) $11250C$ 131. $Consider four conducting materials copper, tungsten, mercury and aluminium with resistivity ρ_{c}, ρ_{T}, ρ_{M} and ρ_{A} respectively$ (1) $ρ_{M} > ρ_{A} > ρ_{C}$ (2) $ρ_{C} > ρ_{A} > ρ_{T}$ (3) $ρ_{A} > ρ_{M} > ρ_{C}$ (4) $ρ_{A} > ρ_{T} > ρ_{C}$ 132. $The four bands of a colour coded resistor are of the colours grey, red, gold and gold. The value of the resistance of the resistor is$ (1) $5.2Ω \pm 5 %$ (2) $82Ω \pm 10 %$ (3) $8.2Ω \pm 5 %$ (4) $82Ω \pm 5 %$ 133. $10 resistors, each of resistance R are connected in series to a battery of emf E and negligible internal resistance. Then, those are connected in parallel to the same battery, the current is increased n times. The value of n is [NEET 2023]$ (1) $100$ (2) $1$ (3) $1000$ (4) $10$ 134. $Two wires of the same metal have same length, but their cross‐sections are in the ratio 3: 1. They are joined in series. The resistance of thicker wire is 10 Ω . The total resistance of the combination will be$ (1) $40Ω$ (2) $100Ω$ (3) $(5/2) Ω$ (4) $(40/3) Ω .$ 135. $To determine the internal resistance of a cell by using a potentiometer the null point is at 1 m when the cell is shunted by 3Ω resistance and at a length 1.5 m . When cell is shunted by 6Ω resistance, the internal resistance of the cell is$ (1) $4Ω$ (2) $8Ω$ (3) $3Ω$ (4) $6Ω$ 136. $A current of 5 A is passing through a metallic wire of cross sectional area 4 \times 10^{- 6} m^{2} . If the density of charge carriers of the wire is 5 \times 10^{26} m^{- 3}, the drift velocity of the electrons will be$ (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) $1 \times 10^{- 2} m s^{- 1} .$ 137. $A 30 V, 90 W lamp is to be operated on a 120 V D.C. line. For proper glow, a resistor of ohm should be connected in series with the lamp.$ (1) $40$ (2) $10$ (3) $20$ (4) $30$ 138. $A car battery of emf 12 V and internal resistance 5 \times 1 0^{- 2} Ω, receives a current of 60 amp from external source, then terminal potential difference of battery is$ (1) $12 V$ (2) $9 V$ (3) $15 V$ (4) $20 V$ 139. $The charge flowing in a conductor changes with time as Q (t) = αt - β t^{2} + γ t^{3} . Where α, β and γ are constants. Minimum value of current is:$ (1) $α - \frac{3 β ^{2}}{γ}$ (2) $α - \frac{γ ^{2}}{β}$ (3) $β - \frac{α ^{2}}{3 γ}$ (4) $α - \frac{β ^{2}}{3 γ}$ 140. $The charge following through a resistance R varies with time t as Q = at - b t^{2}, where a and b are positive constants. The total heat produced in R is$ (1) $\frac{a ^{3} R}{3 b}$ (2) $\frac{a ^{3} R}{2 b}$ (3) $\frac{a ^{3} R}{b}$ (4) $\frac{a ^{3} R}{6 b}$ 141. $A moving coil galvanometer, having a resistance G, produces full scale deflection when a current I_{g} flows through it. This galvanometer can be converted into (i) an ammeter of range 0 to I_{0} (I_{0} > I_{g}) by connecting a shunt resistance R_{A} to it and (ii) into a voltmeter of range 0 to V (V = G I_{0}) by connecting a series resistance R_{v} to it. Then,$ (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) $R_{A} R_{V} = G^{2} and \frac{R _{A}}{R _{V}} = \frac{I _{g}}{( I _{0} - I _{g} )}$ 142. $A uniform metal wire carries a current of 2 A when an ideal cell of 3.4 V is connected across it. The wire has mass 8.92 \times 10^{- 3} kg, density 8.92 \times 10^{3} kgm^{- 3} and resistivity 1.7 \times 10^{- 8} Ωm . Then the length of the wire is$ (1) $5 m$ (2) $6.8 m$ (3) $10 m$ (4) $15.6 m$ 143. $Two electric resistors have equal values of resistance R. Each can be operated with a power of 320 watts (W) at 220 volts. If the two resistors are connected in series to a 110 volts electric supply, then the power generated in each resistor is$ (1) $90 watts$ (2) $80 watts$ (3) $60 watts$ (4) $20 watts$ 144. $Drift speed of electrons, when 1.5 A of current flows in a copper wire of cross section 5 mm^{2}, is v. If the electron density in copper is 9 \times 10^{28} / m^{3} the value of v in mm / s close to (Take charge of electron to be = 1.6 \times 10^{- 19} C)$ (1) $0.02$ (2) $3$ (3) $2$ (4) $0.2$ 145. $A galvanometer of resistance 100Ω when connected in series with 400Ω measures a voltage of upto 10 V . The value of resistance required to convert the galvanometer into ammeter to read upto 10 A is x \times 10^{- 2} Ω . The value of x is:$ (1) $2$ (2) $800$ (3) $20$ (4) $200$ 146. $Two identical heater filaments are connected first in parallel and then in series. At the same applied voltage, the ratio of heat produced in same time for parallel to series will be:$ (1) $1 : 4$ (2) $4 : 1$ (3) $2 : 1$ (4) $1 : 2$ 147. $A charged particle having drift velocity of 7.5 \times 10^{- 4} ms^{- 1} in an electric field of 3 \times 10^{- 10} Vm^{- 1}, has a mobility (in m^{2} V^{- 1} s^{- 1}) of [NEET 2020]$ (1) $2.5 \times 10^{6}$ (2) $2.5 \times 10^{- 6}$ (3) $2.25 \times 10^{- 15}$ (4) $2.25 \times 10^{15}$ 148. $You are given several identical resistances each of value R = 10Ω and each capable of carrying a maximum current of one ampere. It is required to make a suitable combination of these resistances of 5 Ω which can carry a current of 4 ampere. The minimum number of resistances of the type R that will be required for this job is$ (1) $4$ (2) $10$ (3) $8$ (4) $20$ 149. $A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf ‘s is$ (1) $3 : 4$ (2) $3 : 2$ (3) $5 : 1$ (4) $5 : 4$ 150. $A cylindrical wire is stretched up to twice of its length, then its resistance becomes:$ (1) $4 times$ (2) $unchanged$ (3) $\frac{1}{2} times$ (4) $2 times$