STD 12 - Current electricity PYQs: JEE Mains Physics

Showing 1–50 of 311 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. A cylindrical conductor of length 2m and area of cross-section \( 0.2\,mm^{2} \) carries an electric current of 1.6 A when its ends are connected to a 2V battery. Mobility of electrons in the conductor is \( \alpha\times10^{-3} m^{2}/V.s \). The value of \( \alpha \) is:
   (electron concentration \( =5\times10^{28}/m^{3} \) and electron charge \( =1.6\times10^{-19} C \)) 2026 Easy
3. 3. A meter bridge with two resistances \( R_{1} \) and \( R_{2} \) as shown in figure was balanced (null point) at 40 cm from the point P. The null point changed to 50 cm from the point P, when 16 \( \Omega \) resistance is connected in parallel to \( R_{2} \). The values of resistances \( R_{1} \) and \( R_{2} \) are __________ .
   
   2026 Hard
4. 4. A regular hexagon is formed by six wires each of resistance \(r \Omega\) and the corners are joined to centre by wires of same resistance. If the current enters at one corner and leaves at the opposite corner, the equivalent resistance of the hexagon between the two opposite corners will be 2026 Easy
5. 5. A wheatstone bridge is initially at room temperature and all arms of the bridge have same value of resistances ( \(R_1=R_2=R_3=R_4\) ). When \(R_3\) resistance is heated to some temperature, its resistance value has gone up by \(10 \%\). The potential difference \(\left( V _{ a }- V _{ b }\right)\) (after \(R _3\) is heated) is ___________ V.
   2026 Easy
6. 6. A wire of uniform resistance \(\lambda \Omega / m\) is bent into a circle of radius \(r\) and another piece of wire with length 2 r is connected between points A and B \(( AOB )\) as shown in figure. The equivalent resistance between points A and B is ___________\(\Omega\).
   2026 Easy
7. 7. 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
8. 8. For the two cells having same EMF E and internal resistance r, the current passing through the external resistor 6 \(\Omega\) is same when both the cells are connected either in parallel or in series. The value of internal resistance r is ___________ \(\Omega\). 2026 Hard
9. 9. In a meter bridge experiment to determine the value of unknown resistance, first the resistances \(2 \Omega\) and \(3 \Omega\) are connected in the left and right gaps of the bridge and the null point is obtained at a distance \(l cm\) from the left. Now when an unknown resistance \(x \Omega\) is connected in parallel to \(3 \Omega\) resistance, the null point is shifted by 10 cm to the right of wire. The value of unknown resistance \(x\) is _________ \(\Omega\). 2026 Medium
10. 10. In the potentiometer, when the cell in the secondary circuit is shunted with 4 \(\Omega\) resistance, the balance is obtained at the length 120 cm of wire. Now when the same cell is shunted with 12 \(\Omega\) resistance, the balance is shifted to a length of 180 cm. The internal resistance of cell is ___________ \(\Omega\). 2026 Medium
11. 11. Refer to the circuit diagram given below. The heat generated across the \(6\,\Omega\) resistance in \(100\) second is \(\dfrac{\alpha}{100}\) J. The value of \(\alpha\) is _______. (Nearest integer)
    2026 Hard
12. 12. Refer to the figure given below, current between terminals \(A\) and \(B\) is _____ A.
    2026 Hard
13. 13. Refer to the figure given below. The values of \(I_1\), \(I_2\) and \(I_3\) are __________.
    2026 Hard
14. 14. The equivalent resistance between the points \(A\) and \(B\) in the following circuit is \(\frac{x}{5} \Omega\). The value of \(x\) is ___________.
    2026 Hard
15. 15. 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
16. 16. The total length of potentiometer wire AB is 50 cm in the arrangement as shown in figure. If P is the point where the galvanometer shows zero reading then the length AP is _________ cm .
    2026 Hard
17. 17. The voltage and the current between \(A\) and \(B\) points shown in the circuit are _____.
    2026 Hard
18. 18. To compare EMF of two cells using potentiometer the balancing lengths obtained are 200 cm and 150 cm . The least count of scale is 1 cm . The percentage error in the ratio of EMFs is ___________. 2026 Medium
19. 19. Two cells of emfs \(1\) V and \(2\) V and internal resistance \(2\,\Omega\) and \(1\,\Omega\), respectively connected in parallel, gave a current of \(1\) A through an external resistance. If the polarity of one cell is reversed, then value of current through the external resistance will be \(\dfrac{\alpha}{5}\) A. The value of \(\alpha\) is __________. 2026 Hard
20. 20. Two known resistance of \(R \Omega\) and \(2 R \Omega\) and and one unknown resistance \(X \Omega\) are connected in a circuit as shown in the figure. If the equivalent resistance between points A and B in the circuit is \(X \Omega\), then the value of X is _________ \(\Omega\).
    2026 Hard
21. 21. Two resistors \(2 \Omega\) and \(3 \Omega\) are connected in the gaps of bridge as shown in figure. The null point is obtained with the contact of jockey at some point on wire XY . When an unknown resistor is connected in parallel with \(3 \Omega\) resistor, the null point is shifted by 22.5 cm toward Y . The resistance of unknown resistor is _________ \(\Omega\).
    2026 Medium
22. 22. Two resistors of \(200 \, \Omega\) and \(400 \, \Omega\) are connected in series with a battery of \(100\) V. A bulb rated at \(200\) V, \(100\) W is connected across the \(400 \, \Omega\) resistance. The potential drop across the bulb is _______ V. 2026 Hard
23. 23. When an external resistance of \(5\ \Omega\) is connected across terminals of a cell, a current of \(0.25\text{ A}\) flows through it. When the \(5\ \Omega\) resistor is replaced by a \(2\ \Omega\) resistor, a current of \(0.5\text{ A}\) flows through it. The internal resistance of the cell is _______ \(\Omega\). 2026 Easy
24. 24. 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
25. 25. A parallel plate capacitor of area \(A=16 \mathrm{~cm}^2\) and separation between the plates 10 cm , is charged by a DC current. Consider a hypothetical plane surface of area \(\mathrm{A}_0=3.2 \mathrm{~cm}^2\) inside the capacitor and parallel to the plates. At an instant, the current through the circuit is 6A. At the same instant the displacement current through \(\mathrm{A}_0\) is ________ mA . 2025 Medium
26. 26. A wire of length 25 m and cross-sectional area \(5 \mathrm{~mm}^2\) having resistivity of \(2 \times 10^{-6} \Omega \mathrm{~m}\) is bent into a complete circle. The resistance between diametrically opposite points will be: 2025 Medium
27. 27. A wire of resistance \(9 \Omega\) is bent to form an equilateral triangle. Then the equivalent resistance across any two vertices will be _____ ohm. 2025 Easy
28. 28. A wire of resistance \(R\) is bent into a triangular pyramid as shown in figure with each segment having same length. The resistance between points \(A\) and \(B\) is \(R / n\). The value of \(n\) is :
    2025 Medium
29. 29. A wire of resistance R is bent into an equilateral triangle and an identical wire is bent into \(a\) square. The ratio of resistance between the two end points of an edge of the triangle to that of the square is: 2025 Medium
30. 30. Current passing through a wire as function of time is given as \(\mathrm{I}(\mathrm{t})=0.02 \mathrm{t}+0.01 \mathrm{~A}\). The charge that will flow through the wire from \(t=1 s\) to \(t=2 s\) is : 2025 Medium
31. 31. Find the equivalent resistance between two ends of the following circuit
    2025 Easy
32. 32. Given below are two statements :
    Statement-I : The equivalent emf of two nonideal batteries connected in parallel is smaller than either of the two emfs.
    Statement-II : The equivalent internal resistance of two nonideal batteries connected in parallel is smaller than the internal resistance of either of the two batteries.
    In the light of the above statements, choose the correct answer from the options given below. 2025 Medium
33. 33.
    Sliding contact of a potentiometer is in the middle of the potentiometer wire having resistance \(R_p=1 \Omega\) as shown in the figure. An external resistance of \(R_e=2 \Omega\) is connected via the sliding contact. The electric current in the circuit is : 2025 Medium
34. 34. The difference of temperature in a material can convert heat energy into electrical energy. To harvest the heat energy, the material should have _________. 2025 Easy
35. 35. The value of current I in the electrical circuit as given below, when potential at A is equal to the potential at B, will be ____ A.
    2025 Medium
36. 36. 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
37. 37. Two cells of emf 1 V and 2 V and internal resistance \(2 \Omega\) and \(1 \Omega\), respectively, are connected in series with an external resistance of \(6 \Omega\). The total current in the circuit is \(\mathrm{I}_1\). Now the same two cells in parallel configuration are connected to same external resistance. In this case, the total current drawn is \(I_2\). The value of \(\left(\frac{I_1}{I_2}\right)\) is \(\frac{x}{3}\). The value of \(x\) is _____. 2025 Medium
38. 38. 12 wires each having resistance \(2 \Omega\) are joined to form a cube. A battery of \(6 \mathrm{~V}\) emf is joined across point \(\mathrm{a}\) and \(\mathrm{c}\). The voltage difference between \(e\) and \(f\) is ______V.
    2024 Hard
39. 39. A galvanometer ( \(G\) ) of \(2 \Omega\) resistance is connected in the given circuit. The ratio of charge stored in \(C_1\) and \(C_2\) is _______.
    2024 Medium
40. 40. 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
41. 41. A potential divider circuit is shown in figure. The output voltage \(V_0\) is _______.
    2024 Hard
42. 42. A wire of length \(10 \mathrm{~cm}\) and radius \(\sqrt{7} \times 10^{-4} \mathrm{~m}\) connected across the right gap of a meter bridge. When a resistance of \(4.5 \ \Omega\) is connected on the left gap by using a resistance box, the balance length is found to be at \(60 \mathrm{~cm}\) from the left end. If the resistivity of the wire is \(\mathrm{R} \times 10^{-7} \Omega \mathrm{m}\), then value of \(\mathrm{R}\) is : 2024 Hard
43. 43. A wire of resistance \(20 \Omega\) is divided into \(10\) equal parts. A combination of two parts are connected in parallel and so on. Now resulting pairs of parallel combination are connected in series. The equivalent resistance of final combination is _______\(\Omega\). 2024 Hard
44. 44. A wire of resistance \(R\) and length \(L\) is cut into 5 equal parts. If these parts are joined parallely, then resultant resistance will be _______. 2024 Medium
45. 45. A wire of resistance \(R\) and radius \(r\) is stretched till its radius became \(r / 2\). If new resistance of the stretched wire is \(xR\), then value of \(x\) is _______. 2024 Hard
46. 46. 1. A wire of resistance \( R \) and length \( L \) is cut into 5 equal parts. If these parts are joined in parallel, then the resultant resistance will be: 2024 Hard
47. 47. 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
48. 48. An electric toaster has resistance of \(60\  \Omega\) at room temperature \(\left(27^{\circ} \mathrm{C}\right)\). The toaster is connected to a \(220 \mathrm{~V}\) supply. If the current flowing through it reaches \(2.75 \mathrm{~A}\), the temperature attained by toaster is around _______. (if \(\alpha=2 \times 10^{-4} /{ }^{\circ} \mathrm{C}\) ) 2024 Hard
49. 49. At room temperature \(\left(27^{\circ} \mathrm{C}\right)\), the resistance of a heating element is \(50 \Omega\). The temperature coefficient of the material is \(2.4 \times 10^{-4}{ }^{\circ} \mathrm{C}^1\). The temperature of the element, when its resistance is \(62 \Omega\) is _______ \({ }^{\circ} \mathrm{C}\). 2024 Hard
50. 50. By what percentage will the illumination of the lamp decrease if the current drops by \(20 \%\) ? 2024 Hard

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