27. Refraction at Plane surfaces and Total internal reflection
28. Refraction through prism and Dispersion of Light
29. Refraction through Lenses
30. Chromatic abberation in Lenses, Optical instruments and Human eye
31. Velocity of Light
32. Photometry
33. Wave nature of Light
34
Electrostatics
34. Charge and Force
35. Electric Field and Potential
36. Capacitance
37
Electrodynamics
37. Electric current
38. Heating Effect of Current
39. Thermoelectricity
40. Chemical effect of Current
41. Meters
42
Electromagnetism
42. Properties of Magnets
43. Magnetic effects of Current
44. Electromagnetic induction
45. Alternating current
46
Modern Physics
46. Cathode rays, Positive rays and Electrons
47. Photoelectric effect
48. X-rays
49. Atomic structure and Spectrum
50. Radioactivity
51. Nuclear physics
52. Semiconductor and Semiconductor devices
53. Diode and Triode valves
54. Logic gates
55. Relativity and Universe
56. Particle physics
57
Electrostatics
35. Electric Field and Potential
1. Which of following is a vector?
[TOE 2012]
a. Electric potential
b. Electric flux
c. Charge density
d. Electric field intensity
(d) Electric field intensity is a vector quantity
2. What is the potential drop across an electric hot plate which draws 5A when its hot resistance is 24Ω?
[IOM 2010]
a. 120V
b. 140V
c. 130V
d. 150V
(a) V = IR = 5 × 24 = 120V
3. A 2μC charge is enclosed by a Gaussian surface of radius 0.5m. If the radius of the Gaussian surface is increased two times, the no. of flux passing through the new surface will be
[MOE 2068]
a. two times
b. the same
c. four times
d. 0.5 time
(b) Gauss's law states flux depends only on enclosed charge
4. A sphere of radius 10cm is charged to a potential of 300volts. The energy of sphere is
[MOE 2068]
a. 5×10−7 J
b. 5×10−6 J
c. 5×10−5 J
d. 5×10−3 J
(c) U = ½CV2 = ½(4πεor)V2 ≈ 5×10−5 J
5. The electric potential at the surface of atomic nucleus (Z = 50) of radius 9×10−15 m is
[MOE 2010]
a. 80 V
b. 8×106 V
c. 9V
d. 6×106 V
(b) V = kQ/r = kZe/r ≈ 8×106 V
6. In a system, the electric field at the origin is along the positive x-axis. A small circle is drawn with the centre as the origin cutting the axes at points A, B, C & D having co-ordinates (a,0), (0,a), (-a,0) and (0,-a) respectively, out of the points on the periphery's of the circle, the potential is minimum at
[KU 2012]
a. A
b. B
c. C
d. D
(c) Potential decreases in direction of electric field
7. The energy density in the electric field created by a point charge falls off with the distance from the point charge as
[KU 2012]
a. r−1
b. r−3
c. r−2
d. r−4
(d) Energy density ∝ E2 ∝ 1/r4
8. If the electric field intensity is 106 V/m, then find the distance between the plates kept at a potential difference of 103 V
[KU 2010]
a. 10−3 m
b. 109 m
c. 1015 m
d. 1039 m
(a) E = V/d ⇒ d = V/E = 103/106 = 10−3 m
9. NC−1 has the same dimension as
[KU 2009]
a. volt meter
b. farad meter
c. farad/meter
d. volt/meter
(d) Both represent electric field units
10. An α-particle of energy 5MeV is scattered through 180° by a fixed uranium nucleus. The distance of closest approach is of the order of
[BP 2009]
a. 1 Å
b. 10−10 cm
c. 10−12 cm
d. 10−14 cm
(d) r = kq1q2/E ≈ 10−14 cm
11. Which of the rays gets deflected by electric field?
[BP 2012]
a. X-ray
b. α-ray
c. γ-ray
d. UV-rays
(b) α-rays are charged particles (He2+) and get deflected
12. When 1C charge is moved from A to B at the potential of 2V then work done is
[BP 2013]
a. 1 J
b. 2J
c. 5J
d. 1 J
(b) W = qΔV = 1 × 2 = 2J
13. The electric field intensity between two thin metallic plates having surface charge density σ is:
[I.E. 2013]
a. σ/(4πεo)
b. 4πr/(σϵo)
c. σ/ϵo
d. σ/(2ϵo)
(c) For parallel plates E = σ/ϵo
14. Two charges −10C and +10C are placed 10cm apart. The potential at midpoint is:
[I.E. 2011]
a. zero
b. 2V
c. -2V
d. none
(a) Potentials due to equal and opposite charges cancel out
15. Two identical charges +Q are kept at A and B. If we move from A to B, the potential
[I.E. 2009]
a. Decreases continuously
b. Increases continuously
c. First decreases then increases
d. First increases then decreases
(c) Potential is maximum at charges and minimum at midpoint
16. The magnitude of electric field E in the annular region of a charged cylindrical capacitor:
[BP 2014]
a. is same throughout
b. is higher near outer cylinder
c. Varies as 1/r
d. Varies as 1/r2
(c) For cylindrical geometry E ∝ 1/r
17. The electric lines of force about a negative point charge are:
[MOE 2014]
a. Circular, anticlockwise
b. Circular, clockwise
c. Radial, inward
d. Radial, outward
(c) Field lines converge on negative charges
18. A body of mass 1kg carrying 1C charge falls through 1V potential difference. Its velocity is
[MOE 09]
a. 1 ms−1
b. 2ms−1
c. 0.5 ms−1
d. 1.4 ms−1
(d) ½mv2 = qV ⇒ v = √(2qV/m) ≈ 1.4 m/s
19. An electron at rest in electric field between plates separated by 'd' with potential 'V' experiences force:
[KU 2010]
a. eV/d
b. ed/V
c. d/qV
d. V/d
(a) F = eE = e(V/d)
20. The force between two charges in air is 10N. On inserting dielectric, it becomes 4N. Dielectric constant is
[Bangladesh 09]
a. 2.5
b. 0.5
c. 2
d. 4
(a) k = Fair/Fmedium = 10/4 = 2.5
21. The potential difference between two plates separated by 1mm is 100V, the electric field is
[KU 08]
a. 10−10 V/m
b. 105 V/m
c. 103 V/m
d. 10−3 V/m
(b) E = V/d = 100/10−3 = 105 V/m
22. A strong magnetic field is applied on a stationary electron then electron
a. Moves in direction of field
b. Moves opposite to field
c. Remains stationary
d. Moves in helical path
(c) Stationary charge experiences no magnetic force
23. NC-1 has same unit as
[MOE 2056]
a. Volt-meter
b. Volt/meter
c. Farad-meter
d. Farad/meter
(b) Both represent electric field units
24. Two charges +4C and -10C are 7cm apart. Distance from +4C where potential is zero is
[MOE 055]
a. 5 cm
b. 4 cm
c. 3 cm
d. 2 cm
(d) V = k[4/x - 10/(7-x)] = 0 ⇒ x = 2cm
25. A charge in isotropic, homogeneous medium has equipotential surface that is
[MOE 2061]
a. spherical
b. cylindrical
c. elliptical
d. parabolic
(a) For point charge, equipotentials are spherical
26. The energy per unit volume in electric field is given by:
[MOE 2060]
a. E2/ϵo
b. ϵoE2
c. 2ϵoE2
d. ½ϵoE2
(d) Energy density u = ½ϵoE2
27. A charged particle of mass 1g is in equilibrium between plates with E=104 V/m. Its charge is
[MOE 2058]
a. 100 μC
b. 1000 μC
c. 10 μC
d. 1 μC
(b) qE = mg ⇒ q ≈ 1000 μC
28. If potential of small drop is Vo and n drops coalesce, final potential is
[MOE 2008]
a. V=n1/3Vo
b. V=n2/3Vo
c. V=Vo
d. V=n5/3Vo
(b) V ∝ Q/R ∝ n/(n1/3) = n2/3
29. A surface encloses an electric dipole. The flux through the surface is
