1. Two particles have charges in the ratio 1 : 1 and masses in the ratio 2 : 1. They are released from rest in a uniform electric field and move under the influence of the field. The ratio of their kinetic energies of any time will be
Ans: 1 : 2
Hint: F = QE = constant. As they experience same force for same time, their 'P' values are equal, So 
2. Surface charge density of a uniform hollow conducting sphere of radius 10 cm is 8.85 × 10-8 cm-2. The electric potential at centre of the sphere is
Ans: 1000 V
3. In an electric field the electric potential 'V' in volts varies with 'x' in metre according to the equation V = (4x2 + 5). The magnitude of force experienced by a negative charge of 2 μC located at x = 0.5 m is
Ans: 8 × 10-6
Hint: 
4. Concentric conducting spherical shells with inner shell radius 'r' and outer shell 'R'. Outer shell is charged and the inner shell is earthed. The capacity of the system is
Ans: 
Hint: 
q = induced charge on inner surface of outer shell
5. In an electric field some equi-potential surfaces are shown in the figure. The magnitude and direction of the electric field
Ans: 200 Vm-1, 120° from X-axis
Hint: 
is perpendicular to the equi-potential surfaces. In the direction of , potential decreases and 
ΔV = p.d b/n adjacent equi-potential surfaces
Δx = perpendicular distance b/n adjacent equi-potential surfaces
6. A cube has edge 'l'. Imagine a uniform charge distribution along a straight line of 'λ' coulombs per metre. The straight line passes through centre of the cube. The ratio of maximum to minimum electric flux associated with the cube isis
Ans:
Hint:
7. A potential difference of 'V' volt is applied between the two ends of a copper wire of length 'l' metre. If 'μ' the electron mobility in copper, the drift speed of the electrons is
Ans: 
Hint: 
8. Two resistors 20 kΩ and 60 kΩ are connected in series. The free ends of 20 kΩ and 60 kΩ are at - 5 V and + 15 V potentials respectively. The potential at the junction is
Ans: zero
Hint: Current through 20 kΩ = current through 60 kΩ
9. A metal block has dimensions 10 cm × 5 cm × 2 cm. The ratio of maximum to minimum resistance that can be obtained from it is
Ans: 25 : 1
Hint: 
10. Twenty four identical cells each of emf 1.5 V and internal resistance 0.5 Ω are to be connected to a 3 Ω resistance. For maximum current through this resistance, the number of rows and number of columns that you connect these cells will be
Ans: 12 cells in series in each row, 2 rows in parallel
Hint: Max. current through load of RΩ 
11. A resistance of 2Ω is connected across one gap of a metre bridge (the length of bridge wire is 100 cm) and an unknown resistance greater than 2 Ω is connected across the other gap. When these resistances are interchanged, the balance point shifts by 20 cm. Neglecting end corrections, the unknown resistance is
Ans: 3 Ω
Hint:
12. A battery of negligible resistance is connected with 10 m long potentiometer wire. A standard cell in secondary gets balanced against 6 m length of this wire. On increasing the length of potentiometer wire by 2 m and with the same standard cell in the secondary, the increase in balancing length will be
Ans: 1.2 m
Hint: 
13. The cold junction of a thermocouple is kept at 0°C. When its hot junction is kept at θ°C the thermo emf is maximum and is equal to 'e'. Keeping cold junction at 0°C, when the hot junction temperature is 2θ, the thermo emf generated in the thermo couple will be
Ans: zero
Hint:
14. Read the following statements and identify the correct one.
A: Copper exhibits positive Thomson effect.
B: Iron exhibits negative Thomson effect.
C: Lead does not exhibit Thomson effect.
Ans: A, B & C are true
Hint: Thomson Coeff. = σ for copper σ is +ve, for iron σ is -ve & for lead σ is zero
