# 600+ Electromagnetics Solved MCQs

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201.

## Which capacitors relatively costly?

A. electrolyte capacitor
B. mica capacitor
C. air capacitor
D. glass capacitor
202.

## capacitors have a high leakage voltage.

A. electrolyte capacitor
B. variable capacitor
C. "c) air capacitor
D. polyester capacitor
203.

A. 60 n
B. 30 n
C. 40 n
D. 15 n
204.

A. 400 n/c
B. 600 n/c
C. 800 n/c
D. 1200 n/c
205.

## The lines of force due to charged particles are

A. always straight
B. always curved
C. sometimes curved
D. none of the above
206.

## 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
207.

## 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
208.

## 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
209.

## 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
210.

## 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
211.

A. 0.024 f
B. 0.12 f
C. 0.6 f
D. 0.8 f
212.

## 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
213.

A. volts/coulomb
B. coulombs/volt
C. ohms
D. henry/wb
214.

A. 20 uf
B. 30 ue
C. 40 uf
D. 50 uf
215.

## A dielectric material must be

A. resistor
B. insulator
C. good conductor
D. semi conductor
216.

## Which of the following is not a vector ?

A. linear momentum
B. angular momentum
C. electric field
D. electric potential
217.

## 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
218.

## 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
219.

A. 0.0002
B. 0.002
C. 0.02
D. 0.2
220.

## 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
221.

## 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
222.

## 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
223.

A. E = D/E
B. E = D2/t
C. E = jtD
D. E = nD2
224.

## In a capacitor the electric charge is stored in

A. metal plates
B. dielectric
C. both (a) and (6)
D. none of the above
225.

A. glass
B. vacuum
C. ceramics
D. oil
226.

## 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
227.

## 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
228.

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

A. mica capacitor
B. electrolytic capacitor
C. ceramic capacitor
D. paper capacitor
229.

A. small
B. very small
C. large
D. zero
230.

## 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
231.

## 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
232.

## 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
233.

## 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
234.

A. tubes
B. rolled foil
C. disc
D. meshed plates
235.

## 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
236.

A. henry
B. ohm
237.

## 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
238.

A. cv2
B. c2v
C. cv2
D. cv
239.

## Electric field intensity is a quantity

A. scalar
B. vector
C. both (a) and (6)
D. none of the above
240.

A. 2 joules
B. 4 joules
C. 6 joules
D. 8 joules
241.

## The capacitor preferred for high frequency circuits is

A. air capacitor
B. mica capacitor
C. electrolytic capacitor
D. none of the above
242.

A. kw
B. kva
C. kvar
D. volts
243.

## 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
244.

A. 800 uc
B. 900 uc
C. 1200 uc
D. 1600 uc
245.

## 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
246.

A. 50 pf
B. 100 pf
C. 150 pf
D. 200 pf
247.

## 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
248.

A. ceramics
B. oil
C. glass
D. paper
249.

A. mica
B. paper
C. ceramic
D. electrolytic
250.

A. 200
B. 100
C. 3 to 8
D. 1 to 2
251.

A. zero
B. 1
C. 4
D. 10
252.

A. air
B. paper
C. mica
D. electrolytic
253.

## 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
254.

## 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
255.

## 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
256.

## 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
257.

A. coulomb/metre
B. coulomb/metre
C. coulomb/metre
D. coulomb/metre
258.

A. 0.1 to 0.4
B. 0.5 to 1.0
C. 2.0 to 4.0
D. 5 to 100
259.

A. ceramic
B. paper
C. air
D. electrolytic
260.

A. air
B. mica
C. plastic film
D. ceramic
261.

A. reluctance
B. conductance
C. susceptance
D. elastance
262.

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

A. uniform
B. non-uniform
C. zero
D. any of the above
263.

## 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
264.

## field is associated with the capacitor.

A. electric
B. magnetic
C. both (a) and (b)
D. none of the above
265.

A. 50 joules
B. 150 joules
C. 200 joules
D. 250 joules
266.

## 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
267.

A. current
B. voltage
D. charge
268.

A. f/m
B. m/f
C. wb/m
D. no units
269.

## 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
270.

## A unit tube of flux is known as tube

A. newton
C. michale
D. none of the above
271.

## 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
272.

## 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
273.

## Electric displacement is a            quantity.

A. scalar
B. vector
C. both of the above
D. none of the above
274.

A. v/m
B. v2/m
C. m/v
D. m/v2
275.

## Dielectric strength with increasing thickness

A. increases
B. decreases
C. remains unaltered
D. none of the above
276.

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

A. capacitance
B. charge
C. energy
D. none of the above
277.

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

A. inductance
B. capacitance
D. none of the above
278.

A. 0.2 s
B. 0.4 s
C. 0.6 s
D. 0.8 s
279.

A. earth
B. conduction
C. sheath
D. insulator
280.

A. 37, initial
B. 63.2, initial
C. 63.2, final
D. 37, final
281.

A. 37
B. 42
C. 63
D. 73
282.

## 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
283.

C. weber/metre
D. weber/sq-m
284.

## What will happen to an insulating medium if voltage more than the breakdown voltage is applied on it ?

A. it will become magnetic
B. it will melt
C. it will get punctured or cracked
D. its molecular structure will get changed
Answer» C. it will get punctured or cracked
285.

A. paraffin wax
B. quartz
C. glass
D. air
286.

## One volt is the same as

A. one joule/coulomb
B. one coulomb/joule
C. one coulomb
D. one joule
287.

A. cir
B. 1/rc
C. rc
D. ric
288.

## The bridge used for the measurement of the value of the capacitance is

A. wien\s bridge
B. wheatstone bridge
C. schering bridge
D. hay\s bridge
289.

## If an ohmmeter reading immediately goes practically to zero and stays there, capacitor is

A. charged
B. short-circuited
C. lossy
D. satisfactory
290.

## Out of the following capacitors of identical rating which one will have the smallest dimensions ?

A. aluminium foil capacitor
B. mica capacitor
C. ceramic capacitor
D. paper capacitor
291.

## Mica capacitors are characterised by all of thte following except

A. stable operation
B. accurate value
C. low leakage reactance
D. low losses
292.

A. 100 kv/m
B. 10 kv/m
C. 5 kv/m
D. 2 kv/m
293.

A. infinity
B. few kilo ohms
C. few megaahms
D. zero
294.

## Which of the following statements is correct ?

A. mica capacitors are available in capacitance values of 5 to 20 \\if
B. air capapitors have a black band to indicate the outside foil
C. electrolytic capacitors must be connected in correct polarity
D. ceramic capacitors must be con¬nected in correct polarity
Answer» C. electrolytic capacitors must be connected in correct polarity
295.

## Which of the following capacitors preferred for high frequency circuits ?

A. air capacitor
B. electrolytic capacitor
C. mica capacitor
D. none of the above
296.

## An electrolytic capacitor is generally made to provide

A. low capacitance
B. fixed capacitance
C. variable capacitance
D. large value of capacitance
Answer» D. large value of capacitance
297.

## In order to remove static electricity from machinery

A. construct insulated cabins
B. insulate the machinery
C. ground the framework
D. humidify the surroundings
298.

## If a third equal and similar charge is placed between two equal and similar charges, then this third charge will

A. move out of the field of influence of the two charges
B. remain in stable equilibrium
C. not be in equilibrium
D. be in unstable equilibrium
Answer» B. remain in stable equilibrium
299.

## A region around a stationary electric charge has

A. an electric field
B. a magnetic field
C. both (a) and (b)
D. none of the above
300.

## The minimum value of potential gradient in a cable occurs in

A. insulation
B. conductor
C. outer sheath
D. uniformly all over