# 290+ Electromagnetic Theory Solved MCQs

Chapters

35
55.5k
Chapter: Electrostatics
1.

A. 60 N
B. 30 N
C. 40 N
D. 15 N
2.

A. 400 N/C
B. 600 N/C
C. 800 N/C
D. 1200 N/C
3.

## The lines of force due to charged particles are

A. always straight
B. always curved
C. sometimes curved
D. none of the above
4.

## The electric field at a point situated at a distance d from straight charged conductor is

A. proportional to d
B. inversely proportional to d
C. inversely proportional to d
D. none of the above
Answer» B. inversely proportional to d
5.

## The direction of electric field due +0 positive charge is .

A. away from the charge
B. towards the charge
C. both (a) and (6)
D. none of the above
Answer» A. away from the charge
6.

## A field line and an equipotential surface are

A. always parallel
B. always at 90°
C. inclined at any angle 0
D. none of the above
7.

## The ability of charged bodies to exert force on 6ne another is attributed to the existence of

A. electrons
B. protons
C. neutrons
D. electric field
8.

## If the sheet of a bakelite is inserted between the plates of an air capacitor, the capacitance will

A. decrease
B. increase
C. remains unchanged
D. become zero
9.

A. 0.024 F
B. 0.12 F
C. 0.6 F
D. 0.8 F
10.

## For making a capacitor, it is better to select a dielectric having

A. low permittivity
B. high permittivity
C. permittivity same as that of air
D. permittivity slightly more than that of air
11.

A. volts/coulomb
B. coulombs/volt
C. ohms
D. henry/Wb
12.

A. 5 uF
B. 30 uF
C. 45 uF
D. 50 uF
13.

A. 20 uF
B. 30 uE
C. 40 uF
D. 50 uF
14.

## A dielectric material must be

A. resistor
B. insulator
C. good conductor
D. semi conductor
15.

## An electrolytic capacitor can be used for

A. D.C. only
B. AC. only
C. both D.C. as well as A.C.
D. none
16.

## The capacitance of a capacitor is not affected by

A. distance between plates
B. area of plates
C. thickness of plates
D. all of the above
17.

## Which of the following is not a vector ?

A. Linear momentum
B. Angular momentum
C. Electric field
D. Electric potential
18.

## Two plates of a parallel plate capacitor after being charged from a constant voltage source are separated apart by means of insulated handles, then the

A. Voltage across the plates increases
B. voltage across the plates decreases
C. charge on the capacitor decreases
D. charge on the capacitor increases
Answer» B. voltage across the plates decreases
19.

## If A.C. voltage is applied to capacitive circuit, the alternating current can flow in the circuit because

A. varying voltage produces the charg¬ing and dicharging currents
B. of high peak value
C. charging current can flow
D. discharge current can flow
Answer» A. varying voltage produces the charg¬ing and dicharging currents
20.

A. 50
B. 100
C. 150
D. 200
21.

## Which of the following statements is correct ?

A. Air capacitors have a blackband to indicate the outside foil
B. Electrolytic capacitor must be con¬nected in the correct polarity
C. Ceramic capacitors must be con¬nected in the correct polarity
D. Mica capacitors are available in capacitance value of 1 to 10 pF
Answer» B. Electrolytic capacitor must be con¬nected in the correct polarity
22.

A. 0.0002
B. 0.002
C. 0.02
D. 0.2
23.

## "The total electric flux through any closed surface surrounding charges is equal to the amount oflcharge enclosed". The above statement is associated with

A. Coulomb's square law
B. Gauss's law
C. Maxwell's first law
D. Maxwell's second law
24.

## Three capacitors each of the capacity C are given. The resultant capacity 2/3 C can be obtained by using them

A. all in series
B. all in parallel
C. two in parallel and third in series with this combination
D. two in series and third in parallel across this combination
Answer» C. two in parallel and third in series with this combination
25.

## For which of the following parameter variation, the capacitance of the capacitor remains unaffected ?

A. Distance between plates
B. Area of the plates
C. Nature of dielectric
D. Thickness of the plates
Answer» D. Thickness of the plates
26.

## Which of the following statement is true ?

A. The current in the discharging capacitor grows linearly
B. The current in the dicharging capacitor grows exponentially
C. The current in the discharging capacitor decays exponentially
D. The current in the discharging capacitor decreases constantly
Answer» B. The current in the dicharging capacitor grows exponentially
27.

A. E = D/E
B. E = D2/t
C. E = jtD
D. E= nD2
28.

## In a capacitor the electric charge is stored in

A. metal plates
B. dielectric
C. both (a) and (6)
D. none of the above
29.

A. Glass
B. Vacuum
C. Ceramics
D. Oil
30.

## Which of the following capacitors will have the least variation ?

A. Paper capacitor
B. Ceramic capacitor
C. Silver plated mica capacitor
D. None of the above
Answer» C. Silver plated mica capacitor
31.

## Which of the following statements is incorrect ?

A. The leakage resistance of ceramic capacitors is generally high
B. The stored energy in a capacitor decreases with reduction in value of capacitance
C. The stored energy in a capacitor increases with applied voltage
D. A wire cable has distributed capacitance between the conductors
Answer» B. The stored energy in a capacitor decreases with reduction in value of capacitance
32.

## Which of the following capacitors has relatively shorter shelf life ?

A. Mica capacitor
B. Electrolytic capacitor
C. Ceramic capacitor
D. Paper capacitor
33.

## The sparking between two electrical contacts can be reduced by inserting a

A. capacitor in parallel with contacts
B. capacitor in series with each contact
C. resistance in line
D. none of the above
Answer» A. capacitor in parallel with contacts
34.

A. small
B. very small
C. large
D. zero
35.

## The power dissipated in a pure capacitor is

A. zero
B. proportional to applied voltage
C. proportional to value of capacitance
D. both (b) and (c) above
36.

## In a capacitive circuit

A. a steady value of applied voltage causes discharge
B. an increase in applied voltage makes a capacitor charge
C. decrease in applied voltage makes a capacitor charge
D. none of the above
Answer» B. an increase in applied voltage makes a capacitor charge
37.

## When a dielectric slab is introduced in a parallel plate capacitor, the potential difference between plates will

A. remain uncharged
B. decrease
C. increase
D. become zero
38.

## Capacitance increases with

A. increase in plate area and decrease in distance between the plates
B. increase in plate area and distance between the plates
C. decrease in plate area and value of applied voltage
D. reduction in plate area and distance between the plates
Answer» A. increase in plate area and decrease in distance between the plates
39.

## A capacitor consists of

A. two insulators separated by a con¬ductor
B. two conductors separated by an in¬sulator
C. two insulators only
D. two conductors only
Answer» B. two conductors separated by an in¬sulator
40.

A. tubes
B. rolled foil
C. disc
D. meshed plates
41.

## Air capacitors are generally available in the range

A. 10 to 400 pF
B. 1 to 20 pF
C. 100 to 900 pF
D. 20 to 100 pF
Answer» A. 10 to 400 pF
42.

A. henry
B. ohm
43.

A. 10 F
B. 10 uF
C. 100 nF
D. 1000 uF
44.

## A capacitor in a circuit became hot and ultimately exploded due to wrong con¬nections, which type of capacitor it could be ?

A. Paper capacitor
B. Ceramic capacitor
C. Electrolytic capacitor
D. Any-of the above
45.

A. CV2
B. C2V
C. CV2
D. CV
46.

## The absolute permittivity of free space is given by

A. 8.854 x 1(T9 F/m)
B. 8.854 x 1(T10 F/m)
C. 8.854 x KT11 F/m
D. 8.854 x 10"12 F/m
Answer» B. 8.854 x 1(T10 F/m)
47.

A. 1
B. 10
C. 100
D. 1000
48.

## Electric field intensity is a quantity

A. scalar
B. vector
C. both (a) and (6)
D. none of the above
49.

A. 2 joules
B. 4 joules
C. 6 joules
D. 8 joules
50.

## The capacitor preferred for high frequency circuits is

A. air capacitor
B. mica capacitor
C. electrolytic capacitor
D. none of the above
51.

A. kW
B. kVA
C. kVAR
D. volts
52.

## While testing a capacitor with ohm-metre, if the capacitor shows charging, but the final resistance reading is appreciably less than normal, it can be concluded that the capacitor is

A. short-circuited
B. open circuited
C. alright
D. leaky
53.

A. 800 uC
B. 900 uC
C. 1200 uC
D. 1600 uC
54.

## Which capacitor will be physically smaller for the same ratings ?

A. Ceramic capacitor
B. Paper capacitor
C. Both will be of equal size
D. None of the above
55.

A. 50 pF
B. 100 pF
C. 150 pF
D. 200 pF
56.

## A mica capacitor and a ceramic capacitor both have the same physical dimensions. Which will have more value of capacitance ?

A. Ceramic capacitor
B. Mica capacitor
C. Both will have identical value of capacitance
D. It depends on applied voltage
57.

A. Ceramics
B. Oil
C. Glass
D. Paper
58.

A. Mica
B. Paper
C. Ceramic
D. Electrolytic
59.

A. 200
B. 100
C. 3 to 8
D. 1 to 2
60.

A. zero
B. 1
C. 4
D. 10
61.

A. Air
B. Paper
C. Mica
D. Electrolytic
62.

## Which of the following capacitors can be used for temperature compensation ?

A. Air capacitor
B. Ceramic capacitor
C. Paper capacitor
D. None of the above
63.

## Which of the following statements is incorrect ?

A. The thinner the dielectric, the more the capacitance and the lower the voltage breakdown rating for a capacitor .
B. A six dot mica capacitor colour coded white, green, black, red and yellow has the capacitance value of 500 pF
C. Capacitors in series provide less capacitance but a higher voltage breakdown rating for the combina¬tion
D. A capacitor can store charge be¬cause it has a dielectric between two conductors
Answer» B. A six dot mica capacitor colour coded white, green, black, red and yellow has the capacitance value of 500 pF
64.

A. ± 5%
B. ± 10%
C. ± 15%
D. ± 20%
65.

## For closer tolerances which of the following capacitors is usually preferred ?

A. Paper capacitor
B. Mica capacitor
C. Ceramic disc capacitor
D. None of the above
66.

## The electrostatic force between two charges of one coulomb each and placed at a distance of 0.5 m will be

A. 36 x 10fa
B. 36 x 107 N
C. 36 x 108 N
D. 36 x 109 N
Answer» D. 36 x 109 N
67.

A. Coulomb/metre
B. Coulomb/metre
C. Coulomb/metre
D. Coulomb/metre
68.

## "The surface integral of the normal component of the electric displacement D over any closed surface equals the charge enclosed by the surface". The above statement is associated with

A. Gauss's law
B. Kirchhoff s law
D. Lenz's law
69.

## Dielectric strength of mica is

A. 10 to 20 kV/mm
B. 30 to 50 kV/mm
C. 50 to 200 kV/mm
D. 300 to 500 kV/mm
Answer» C. 50 to 200 kV/mm
70.

A. 0.1 to 0.4
B. 0.5 to 1.0
C. 2.0 to 4.0
D. 5 to 100
71.

A. Paper
B. Air
C. Mica
D. Electrolytic
72.

A. Air
B. Paper
C. Mica
D. Electrolytic
73.

A. Ceramic
B. Paper
C. Air
D. Electrolytic
74.

A. Air
B. Mica
C. Plastic film
D. Ceramic
75.

A. reluctance
B. conductance
C. susceptance
D. elastance
76.

## When the dielectric is homogeneous,the potential gradient is

A. uniform
B. non-uniform
C. zero
D. any of the above
77.

## The potential gradient across the material of low permittivity is than across the material of high permittivity.

A. smaller
B. greater
C. both (a) and (b)
D. none of the above
78.

## ________field is associated with the capacitor.

A. Electric
B. Magnetic
C. Both (a) and (b)
D. None of the above
79.

A. 50 joules
B. 150 joules
C. 200 joules
D. 250 joules
80.

## A single core cable used on 33000 V has conductor diameter 10 mm and the in¬ternal diameter of sheath 25 mm. The maximum electrostatic stress in the cable is

A. 62 x 105 V/m
B. 72 x 105 V/m
C. 82 x 105 V/m
D. 92 x 105 V/m
Answer» B. 72 x 105 V/m
81.

## Two infinite parallel plates 10 mm apart have maintained between them a potential difference of 100 V. The acceleration of an electron placed between them is

A. 0.56 x 1015 m/s2
B. 1.5 x 1015 m/s2
C. 1.6 x 1015 m/s2
D. 1.76 x 1015 m/s2
Answer» D. 1.76 x 1015 m/s2
82.

A. current
B. voltage
D. charge
83.

A. F/m
B. m/F
C. Wb/m
D. no units
84.

## The phenomenon of an uncharged body getting charged merely by the nearness of a charged body is known as

A. pholoelectric effect
B. chemical effect
C. magnetic effect
D. induction
85.

## A unit tube of flux is known as tube

A. Newton
C. Michale
D. None of the above
86.

## The number of Faraday tubes of flux passing through a surface in an electric field is called

A. electric flux
B. electric flux density
C. magnetic flux density
D. electric charge density
87.

## The value of E within the field due to a point charge can be found with the help of

B. Kirchhoff s laws
C. Coulomb's laws
D. none of the above
88.

## at a point may be defined as equal to the lines of force passing normally through a unit cross section at that point.

A. Electric intensity
B. Magnetic flux density
C. Electric flux
D. None of the above
89.

## Electric intensity at any point in an electric field is equal to the at that point.

A. electric flux
B. magnetic flux density
D. none of the above
90.

## Electric displacement is a______quantity.

A. scalar
B. vector
C. both of the above
D. none of the above
91.

## at a point is equal to the negative potential gradient at that point.

A. Electric intensity
B. Electric flux
C. Magnetic flux
D. Magnetic flux density
92.

A. V/m
B. V2/m
C. m/V
D. m/V2
93.

## Dielectric strength ______ with increasing thickness

A. increases
B. decreases
C. remains unaltered
D. none of the above
94.

## The property of a capacitor to store electricity is called its

A. capacitance
B. charge
C. energy
D. none of the above
95.

## is that property of a capacitor which delays any change of voltage across it.

A. Inductance
B. Capacitance
D. None of the above
96.

A. 0.2 s
B. 0.4 s
C. 0.6 s
D. 0.8 s
97.

A. earth
B. conduction
C. sheath
D. insulator
98.

A. 37, initial
B. 63.2, initial
C. 63.2, final
D. 37, final
99.

A. 37
B. 42
C. 63
D. 73
100.

## A capacitor consists of two

A. ceramic plates and one mica disc
B. insulators separated by a dielectric
C. silver-coated insulators
D. conductors separated by an insulator
Answer» D. conductors separated by an insulator