DEPARTMENT OF SCHOOL EDUCATION, CHENGALPATTU DISTRICT
SECOND ASSESSMENT TEST-JANUARY -2022 REGISTER NUMBER
PHYSICS
CLASS: 12 MAXIMUM MARKS: 70
TIME ALLOWED: 3 HOURS
PART – I (15 × 1 = 15)
Note: Answer all the questions.
Choose the most appropriate answer from the given four alternatives and Write the option code and the corresponding answer.
1. Which charge configuration produces a uniform electric field?
(a) point charge
(b) uniformly charged infinite line
(c) uniformly charged infinite plane
(d) uniformly charged spherical shell
2. If voltage applied on a capacitor is increased from V to 2V, choose the correct conclusion.
(a) Q remains the same, C is doubled
(b) Q is doubled, C doubled
(c) C remains same, Q doubled
(d) Both Q and C remain same
3. A sample of HCl gas is placed in a uniform electric field of magnitude 3 × 104
N C–1. The dipole moment of each
HCl molecule is 3.4 × 10–30 Cm. Calculate the maximum torque experienced by each HCl molecule.
(a) 10.2 × 10+26 Nm
(b) 10.2 × 10-26 Nm
(c) 10.2 × 10+6 Nm
(d) 16.2 × 10-26 Nm
4. Resistance of a material at 200C and 400C are 45 Ω and 85 Ω respectively. Find its temperature coefficient of
resistivity.
(a) 0.4 per0C
(b) 0.0044 per0C
(c) 0.044 per0C
(d) 60.0044 per0C
5. The filament of 50 W and 90 W bulbs are of the same length, then
(a) 50 W filament is thicker
(b) 90 W filament is thicker
(c) both are of same thickness
(d) none of these
6. Two wires of A and B with circular cross section are made up of the same material with equal lengths. Suppose
RA = 3 RB, then what is the ratio of radius of wire A to that of B?
(a) 3
(b) √3
(c) 1/√3
(d) 1/3
7. Moving electric charge produces
(a) both electric and magnetic fields
(b) electric field only
(c) magnetic field only
(d) neither of these two fields
8. A wire of length l carrying a current I along the Y direction is kept in a magnetic field given by B= B/√3 (î+j+k) T .The magnitude of Lorentz force acting on the wire is
(a)√(2/3) BIl
(b)√(1/3) BIl
(c)√(1/2) BIl
(d) √2 BIl
9. If the angular momentum of an electron of mass m, charge e, revolving in a circular orbit is L, then its magnetic
moment is
(a) eLm
(b) eL/m
(c) eL/2m
(d) 2eL/m
10. A step-down transformer reduces the supply voltage from 220 V to 11 V and increase the current from 6 A to 100 A.
Then its efficiency is
(a) 1.2
(b) 0.83
(c) 0.12
(d) 0.9
11. The self-inductance of a straight conductor is :
(a) zero
(b) infinite
(c) very large
(d) very small
12. The flux linked with a coil at any instant t is given by ϕB = 10t2 - 50t + 250. The induced emf at t = 3 s is
(a) -190 V
(b) -10 V
(c) 10 V
(d) 190 V
13. In a series RL circuit, the resistance and inductive reactance are the same. Then the phase difference between the
voltage and current in the circuit is
(a) zero
(b) π/4
(c) π/2
(d) π/6
14. A wire of resistance R is cut into n equal parts. These parts are then connected in parallel with each other. The
equivalent resistance of the combination is
(a) nR
(b) R / n
(c) n / R2
(d) R / n2
15. Two point charges (+e) and (-e) are kept inside metallic cube without touching its sides. Electric flux emerging out of the cube is
(a) zero
(b) 2e / Ꜫo
(c) +e / Ꜫo
(d) -e / Ꜫo
PART – II (6 × 2 = 12)
Note: Answer any six questions. Question number 24 is compulsory
16. State Coulomb's law and write its vector form.
17. A 12 pF capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor?
18. Define temperature co-efficient of the resistance and mention its unit
19. How can you combine three resistances, each of 4 Ω such that the total resistance of the circuit is 6 Ω?
20. State Flemming’s left hand rule
21. How will you increase the current sensitivity of a moving coil galvanometer?
22. Define Q-factor?
23. Find the instantaneous value of alternating voltage v=10sin(3 π × 104
t ) volt at i) 0 s ii) 50 μs
24. An infinite line charge produces a field of 9 × 104 NC-1 at a distance of 2 cm. calculate the linear charge density.
PART – III 6 × 3 = 18
Note: Answer any six questions. Question number 33 is compulsory
25. Define capacitance of the capacitor and write any three uses of the capacitor.
26. Three equal charges of 5 μC each are placed at the three vertices of an equilateral triangle of side 5 cm each. Calculate the electrostatic potential energy of the system of charges.
27. State kirchhoff’s current rule and voltage rule.
28. If the internal resistances of the cells are very low compared to external resistance R, to get the maximum advantage how the cells are supposed to connect? Deduce its expression.
29. Write the properties of magnetic field lines.
30. How is a galvanometer converted into an ammeter?- explain
31. How will you induce an emf by changing the area enclosed by the coil?
32. Mention the various energy losses in a transformer.
33. Two wires A and B of equal masses and of the same material are taken. The diameter of wire A is half the diameter of the wire B. If the resistance of wire A is 24 Ω, calculate the resistance of the wire B.
PART – IV (5 × 5 = 25)
Note: Answer all the questions.
34. A) Calculate the electric field due to a dipole on its axial line
(OR)
B) Derive the expression for the force on a current-carrying conductor in a magnetic field.
35. A) Obtain the condition for bridge balance in Wheatstone’s bridge.
(OR)
B) Derive an expression for phase angle between the applied voltage and current in a series RLC circuit.
36. A) Deduce the relation for the magnetic field at a point due to an infinitely long straight conductor carrying current.
(OR)
B) Explain the determination of the internal resistance of a cell using voltmeter.
37. A) Explain in detail the construction and working of a Van de Graaff generator.
(OR)
B) Derive the expression for the force between two parallel, current-carrying conductors.
38. A) State Gauss law and obtain the expression for electric field due to a charged infinite plane sheet.
(OR)
B) Deduce the expression for Self-inductance of a long solenoid
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