Electrical Energy and Power PYQs: JEE Mains Physics

Showing 1–43 of 43 questions

1. 1. A battery with EMF E and internal resistance r is connected across a resistance R. The power consumption in R will be maximum when : 2026 Easy
2. 2. An electric power line having total resistance of 2 Ω, delivers 1 kW of power of 250 V. The percentage efficiency of transmission line is: __________ . 2026 Hard
3. 3. The heat generated in 1 minute between points A and B in the given circuit, when a battery of 9 V with internal resistance of \(1 \Omega\) is connected across these points is _________ J.
   2026 Hard
4. 4. A motor operating on 100 V draws a current of 1 A. If the efficiency of the motor is \(91.6 \%\), then the loss of power in units of \(\mathrm{cal} / \mathrm{s}\) is _________. 2025 Medium
5. 5. 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 main supply. The total power drawn by the combination is : 2025 Easy
6. 6. A heater is designed to operate with a power of \(1000 \mathrm{~W}\) in a \(100 \mathrm{~V}\) line. It is connected in combination with a resistance of \(10 \Omega\) and a resistance \(R\), to a \(100 \mathrm{~V}\) mains as shown in figure. For the heater to operate at \(62.5 \mathrm{~W}\), the value of \(\mathrm{R}\) should be _______ \(\Omega\).
   2024 Hard
7. 7. An electric bulb rated \(50 \mathrm{~W}-200 \mathrm{~V}\) is connected across a \(100 \mathrm{~V}\) supply. The power dissipation of the bulb is _______. 2024 Hard
8. 8. By what percentage will the illumination of the lamp decrease if the current drops by \(20 \%\) ? 2024 Hard
9. 9. In the following circuit, the battery has an emf of \(2\mathrm{V}\) and an internal resistance of \(\frac{2}{3}\  \Omega\). The power consumption in the entire circuit is _______ \(W\).
   2024 Hard
10. 10. The number of electrons flowing per second in the filament of a \(110 \mathrm{~W}\) bulb operating at \(220 \mathrm{~V}\) is _______. (Given \(\mathrm{e}=1.6 \times 10^{-19} \mathrm{C}\) ) 2024 Hard
11. 11. The ratio of heat dissipated per second through the resistance \(5 \Omega\) and \(10 \Omega\) in the circuit given below is _______.
    2024 Hard
12. 12. Water boils in an electric kettle in \(20\) minutes after being switched on. Using the same main supply, the length of the heating element should be _______ to _______ times of its initial length if the water is to be boiled in \(15\) minutes. 2024 Hard
13. 13. When a potential difference \(V\) is applied across a wire of resistance \(R\), it dissipates energy at a rate \(W\). If the wire is cut into two halves and these halves are connected mutually parallel across the same supply, the same supply, the energy dissipation rate will become what? 2024 Hard
14. 14. A potential \(V_0\) is applied across a uniform wire of resistance \(R\). The power dissipation is \(P_1\). The wire is then cut into two equal halves and a potential of \(V _0\) is applied across the length of each half. The total power dissipation across two wires is \(P_2\). The ratio \(P_2: P_1\) is \(\sqrt{x}: 1\). The value of \(x\) is \(.............\). 2023 Medium
15. 15. Ratio of thermal energy released in two resistor \(R\) and \(3 R\) connected in parallel in an electric circuit is : 2023 Easy
16. 16. 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: 2023 Medium
17. 17. A \(220 \; V , 50 \; Hz\) AC source is connected to a \(25 \; V\), \(5 \; W\) lamp and an additional resistance \(R\) in series (as shown in figure) to run the lamp at its peak brightness, then the value of \(R\) (in ohm) will be
    2022 Medium
18. 18. A resistor develops \(300 \,J\) of thermal energy in \(15 \,s\), when a current of \(2\, A\) is passed through it. If the current increases to \(3 \,A\), the energy developed in \(10\,\,s\)  is........\(J.\) 2022 Medium
19. 19. 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 \(........... W\) 2022 Medium
20. 20. Two coils require \(20\) minutes and \(60\) minutes respectively to produce same amount of heat energy when connected separately to the same source. If they are connected in parallel arrangement to the same source; the time required to produce same amount of heat by the combination of coils, will be________ \(min\) 2022 Hard
21. 21. Water fall from a \(40\,m\) high dam at the rate of \(9 \times 10^{4}\,kg\) per \(hour\). Fifty percentage of gravitational potential energy can be converted into electrical energy. Using this hydroelectric energy number of \(100\,W\) lamps, that can be lit, is (Take \(\left.g=10\,ms ^{-2}\right)\) 2022 Medium
22. 22. A resistor develops \(500\, J\) of thermal energy in \(20 \,s\) when a current of \(1.5\, A\) is passed through it. If the current is increased from \(1.5 \,A\) to \(3\, A\) what will be the energy (in \(J\)) developed in \(20\, s\). 2021 Medium
23. 23. A resistor dissipates \(192\, {J}\) of energy in \(1\, {s}\) when a current of \(4\, {A}\) is passed through it. Now, when the current is doubled, the amount of thermal energy dissipated in \(5 \,{s}\) in \(.....\,J.\) 2021 Medium
24. 24. A uniform heating wire of resistance \(36\, \Omega\) is connected across a potential difference of \(240\, {V}\) The wire is then cut into half and potential difference of \(240\, {V}\) is applied across each half separately. The ratio of power dissipation in first case to the total power dissipation in the second case would be \(1: {x}\), where \({x}\) is........... . 2021 Medium
25. 25. An electric bulb of \(500 \,watt\) at \(100\, volt\) is used in a circuit having a \(200\, {V}\) supply. Calculate the resistance \({R}\) to be connected in series with the bulb so that the power delivered by the bulb is \(500\, {W}\). (in \(\Omega\)) 2021 Medium
26. 26. An electric bulb rated as \(200\, {W}\) at \(100 \,{V}\) is used in a circuit having \(200\, {V}\) supply. The resistance \('R'\) that must be put in series with the bulb so that the bulb delivers the same power is \(.....\,\Omega\) 2021 Medium
27. 27. The energy dissipated by a resistor is \(10 \,mJ\) in \(1\,s\) when an electric current of \(2\, mA\) flows through it. The resistance is \(....... \Omega\) (Round off to the Nearest Integer) 2021 Easy
28. 28. A battery of \(3.0\, V\) is connected to a resistor dissipating \(0.5\, W\) of power. If the terminal voltage of the battery is \(2.5\, V\) the power dissipated within the internal resistance is\(.......W\) 2020 Hard
29. 29. An electrical power line, having a total resistance of \(2 \Omega\), delivers \(1 \,kW\) at \(220\, V\). The efficiency of the transmission line is approximately \(.......\%\) 2020 Medium
30. 30. In a building there are \(15\) bulbs of \(45\; \mathrm{W}, 15\) bulbs of \(100\; \mathrm{W}, 15\) small fans of \(10 \;\mathrm{W}\) and \(2\) heaters of \(1 \;\mathrm{kW}\). The voltage of electric main is \(220\; \mathrm{V}\). The minimum fuse capacity (rated value) of the building will be: .......... \(A\) 2020 Medium
31. 31. Model a torch battery of length \(l\) to be made up of a thin cylindrical bar of radius \('a'\) and a concentric thin cylindrical shell of radius ' \(b\) ' fille in between with an electrolyte of resistivity \(\rho\) (see figure). If the battery is connected to a resistance of value \(R ,\) the maximum Joule heating in \(R\) will take place for
    2020 Hard
32. 32. A cell of internal resistance \(r\) drives current through an external resistance \(R\) . The power delivered by the cell to the external resistance will be maximum when: 2019 Medium
33. 33. A current of \(2\, mA\) was passed through an unknown resistor which dissipated a power of \(4.4\, W\). Dissipated power when an ideal power supply of \(11\, V\) is connected across it is 2019 Medium
34. 34. One \(kg\) of water, at \(20\,^oC\), is heated in an electric kettle whose heating element has a mean (temperature averaged) resistance of \(20\, \Omega \). The rms voltage in the mains is \(200\, V\). Ignoring heat loss from the kettle, time taken for water to evaporate fully, is close to.......... \(\min\) [Specific heat of water \(= 4200\, J/kg\, ^oC\)), Latent heat of water \(= 2260\, k\,J/kg\)] 2019 Hard
35. 35. The resistive network shown below is connected to a \(D.C.\) source of \(16\, V\). The power consumed by the network is \(4\, Watt\). The value of \(R\) is ............. \(\Omega\)
    2019 Medium
36. 36. Two electric bulbs, rated at \((25\, W, 220\, V)\) and \((100\, W, 220\, V)\), are connected in series acroos a \(220\, V\) voltage source. If the \(25\, W\) and \(100\, W\) bulbs draw powers \(P_1\) and \(P_2\) respectively, then 2019 Hard
37. 37. Two equal resistances when connected in series to a battery, consume electric power of \(60\,W.\) If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be .............. \(W\) 2019 Medium
38. 38. The figure shows three circuits \(I, II\) and \(III\) which are connected to a \(3\,V\) battery. If the powers dissipated by the configurations \(I, II\) and \(III\) are \(P_1 , P_2\) and \(P_3\) respectively, then
    2017 Hard
39. 39. In the circuit shown, the resistance \(r\) is a variable resistance. If for \(r = fR,\)  the heat generation in \(r\) is maximum then the value of \(f\) is 
    2016 Hard
40. 40. Four bulbs \(B_1 , B_2, B_3\) and \(B_4\) of \(100\, W\) each are connected to \(220\, V\) main as shown in the figure. The reading in an ideal ammeter will be ............... \(A\)
    2014 Hard
41. 41. In a large building, there are \(15\) bulbs of \(40\ W\), \(5\) bulbs of \(100\ W, 5\) fans of \(80\ W\) and \(1\) heater of \(1\ kW\). The voltage of electric mains is \(220\ V\). The minimum capacity of the main fuse of the building will be ................ \(A\) 2014 Medium
42. 42. The supply voltage to room is \(120\ V\). The resistance of the lead wires is \(6\,\Omega\) . A \(60\ W\) bulb is already switched on. What is the decrease of voltage across the bulb, when a \(240\ W\) heater is switched on in parallel to the bulb? ............. \(V\) 2013 Medium
43. 43. Which of the four resistances \(P, Q, R\) and \(S\) generate the greatest amount of heat when a current flows from \(A\) to \(B\) ?
    2013 Hard

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