# Multiple choice question for engineering

## Set 1

1. In a magnetic material, always there exist magnetic dipoles as well as monopoles. State True/False.

a) True

b) False

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2. Find the total flux in a material of flux density 15 units in an area of 24 units.

a) 3.6

b) 7.2

c) 9.6

d) 5.4

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3. Find the magnetic field intensity of a material with flux density of 24 units in air(in 10^{6} order)

a) 19.09

b) 21

c) 25

d) 26.78

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^{-7}. Thus H = 24/4∏ x 10

^{-7}= 19.09 x 10

^{6}units.

4. Find the magnetic flux density when the vector potential is a position vector.

a) 1

b) 0

c) -1

d) ∞

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5. When the electric field travels in +x direction and the EM wave is travelling the –y direction, then the magnetic field will be travelling in which direction?

a) +z direction

b) –z direction

c) Either +z or –z direction

d) Does not travel

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6. Inductance is present in semiconductor. State True/False.

a) True

b) False

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7. Electromagnetic waves are longitudinal in nature. State True/False.

a) True

b) False

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8. Identify the devices that do not use electromagnetic energy.

a) Television

b) Washing machine

c) Microwave oven

d) Mobile phones

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9. Find the flux density of a conductor in the square of the centre of the loop having current 3.14A and radius is 1.414m in air.

a) 8π x 10^{-7}

b) 4π x 10^{-7}

c) 6π x 10^{-7}

d) 2π x 10^{-7}

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^{-7}x 3.14/π x 1.414 = 8π x 10

^{-7}units.

10. Which type of flux will increase the inductance?

a) Series aiding

b) Series opposing

c) Shunt aiding

d) Shunt opposing

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## Set 2

1. The expression for refractive index is given by

a) N = v/c

b) N = c/v

c) N = cv

d) N = 1/cv

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2. Numerical aperture is expressed as the

a) NA = sin θa

b) NA = cos θa

c) NA = tan θa

d) NA = sec θa

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3. For total internal reflection to occur, which condition must be satisfied?

a) N1 = N2

b) N1 > N2

c) N1 < N2

d) N1 x N2=1

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4. Find the refractive index of a medium having a velocity of 1.5 x 10^{8}.

a) 0.5

b) 5

c) 0.2

d) 2

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^{8}and c = 3 x 10

^{8}, we get n = 3/1.5 = 2. The quantity has no unit.

5. The refractive index of water will be

a) 1

b) 2.66

c) 5

d) 1.33

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^{8}. On substituting for the speed of light, we get refractive index as n = 3/2.25 = 1.33(no unit).

6. The refractive index of air is unity. State True/False.

a) True

b) False

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7. The numerical aperture of a coaxial cable with core and cladding indices given by 2.33 and 1.4 respectively is

a) 3.73

b) 0.83

c) 3.46

d) 1.86

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^{2}– n2

^{2}), where n1 and n2 are the refractive indices of core and cladding respectively. On substituting for n1 = 2.33 and n2 = 1.4, we get NA = √(2.33

^{2}-1.4

^{2}) = 1.86.

8. Find the acceptance angle of a material which has a numerical aperture of 0.707 in air.

a) 30

b) 60

c) 45

d) 90

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^{-1}(NA), put NA = 0.707, thus θa = sin

^{-1}(0.707) = 45 degree.

9. The numerical aperture of a material with acceptance angle of 60 degree in water will be

a) 1.15

b) 2.15

c) 5.21

d) 1.52

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10. The core refractive index should be lesser than the cladding refractive index for a coaxial cable. State True/False

a) True

b) False

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11. The refractive index is 2.33 and the critical angle is 350. Find the numerical aperture.

a) 2

b) 1.9

c) 2.33

d) 12

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12. Choose the optical fibre material from the given materials.

a) Glass

b) Plastic

c) Silica

d) Quartz

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## Set 3

1. The electric flux density and electric field intensity have which of the following relation?

a) Linear

b) Nonlinear

c) Inversely linear

d) Inversely nonlinear

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2. The electric field intensity is the negative gradient of the electric potential. State True/False.

a) True

b) False

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3. Find the electric potential for an electric field 3units at a distance of 2m.

a) 9

b) 4

c) 6

d) 3/2

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4. Find the potential at a point (4, 3, -6) for the function V = 2x^{2}y + 5z.

a) 96

b) 66

c) 30

d) -66

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^{2}y + 5z at the point (4, 3, -6) is given by V = 2(4)2(3) + 5(-6) = 96-30 = 66 units.

5. Find the electric flux density surrounding a material with field intensity of 2xyz placed in transformer oil ( εr = 2.2) at the point P(1,2,3) is

(in 10^{-10} units)

a) 2.1

b) 2.33

c) 2.5

d) 2.77

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^{-12}X 2.2 X 2(1)(2)(3) = 2.33 X 10

^{-10}units.

6. If potential V = 20/(x^{2} + y^{2}). The electric field intensity for V is

40(x i + y j)/(x^{2} + y^{2})^{2}. State True/False.

a) True

b) False

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^{2}+ y

^{2})) = -(-40x i /(x

^{2}+ y

^{2})

^{2}– 40(y j)/(x

^{2}+ y

^{2})

^{2}) = 40(x i + y j)/(x

^{2}+ y

^{2})

^{2}. Thus the statement is true.

7. Find the potential of the function V = 60cos θ/r at the point P(3, 60, 25).

a) 20

b) 10

c) 30

d) 60

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8. Find the work done moving a charge 2C having potential V = 24volts is

a) 96

b) 24

c) 36

d) 48

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9. If the potential is given by, V = 10sin θ cosφ/r, find the density at the point P(2, π/2, 0)

(in 10^{-12} units)

a) 13.25

b) 22.13

c) 26.31

d) 31.52

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^{-12}X 5/2 = 22.13 units.

10. If V = 2x^{2}y + 20z – 4/(x^{2} + y^{2}), find the density at A(6, -2.5, 3) in nC/m^{2}.

a) 0.531i – 0.6373j – 0.177k

b) 0.6373i – 0.177j -0.531k

c) 0.177i – 0.6373j – 0.531k

d) 0.531i – 0.177j – 0.6373k

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^{-12}X (59.97i – 71.98j -20k) = (0.531i – 0.6373j – 0.177k) nC/m

^{2}.

## Set 4

1. Find the resistivity of a material having resistance 20kohm, area 2 units and length of 12m.

a) 6666.6

b) 3333.3

c) 1200

d) 2000

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^{3}, A = 2 and L = 12. We get ρ = 3333.3 units.

2. A resistor value of colour code orange violet orange will be

a) 37 kohm

b) 37 Mohm

c) 48 kohm

d) 48 Mohm

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3. A infinite resistance is considered as a/an

a) Closed path(short circuit)

b) Open path

c) Not defined

d) Ammeter with zero reading

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4. Find the time constant in a series R-L circuit when the resistance is 4 ohm and the inductance is 2 H.

a) 0.25

b) 0.2

c) 2

d) 0.5

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5. Find the time constant for a R-C circuit for resistance R = 24 kohm and C = 16 microfarad.

a) 1.5 millisecond

b) 0.6 nanosecond

c) 384 millisecond

d) 384 microsecond

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^{3}x 16 x 10

^{-6}= 0.384 = 384 millisecond.

6. Find the capacitance when charge is 20 C has a voltage of 1.2V.

a) 32.67

b) 16.67

c) 6.67

d) 12.33

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7. Calculate the capacitance of two parallel plates of area 2 units separated by a distance of 0.2m in air(in picofarad)

a) 8.84

b) 88.4

c) 884.1

d) 0.884

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^{-12}, we get C = 8.841 x 10

^{-11}= 88. 41 pF.

8. Compute the capacitance between two concentric shells of inner radius 2m and the outer radius is infinitely large.

a) 0.111 nF

b) 0.222 nF

c) 4.5 nF

d) 5.4 nF

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^{-12}x 2 = 0.222 nF.

9. The capacitance of a material refers to

a) Ability of the material to store magnetic field

b) Ability of the material to store electromagnetic field

c) Ability of the material to store electric field

d) Potential between two charged plates

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10. A cable of core radius 1.25cm and impregnated paper insulation of thickness 2.13cm and relative permittivity 3.5. Compute the capacitance of the cable/km(in nF)

a) 195.7

b) 179.5

c) 157.9

d) 197.5

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^{-7}= 195.7 nF.

## Set 5

1. The resultant electric field of a wave with Ex = 3 and Ey = 4 will be

a) 7

b) 1

c) 25

d) 5

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^{2}+ Ey

^{2}). On substituting for Ex = 3 and Ey = 4, we get E = 5 units.

2. In S polarisation, the electric field lies in the plane perpendicular to that of the interface. State True/False

a) True

b) False

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3. In P polarisation, the electric field lies in the same plane as the interface. State True/False.

a) True

b) False

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4. The group delay of a wave with phase constant 2.5 units and frequency of 1.2 radian/sec is

a) 3.7

b) 1.3

c) 3

d) 2.08

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5. The Brewster angle is valid for which type of polarisation?

a) S polarised

b) P polarised

c) Elliptical

d) Linear

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6. Find the reflection coefficient of a wave with an incident electric field of 5 units and reflected electric field of 2 units.

a) 2.5

b) 0.4

c) 0.8

d) 1.2

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7. The transmission coefficient of a wave with incident and transmitted electric field of 5 and 5 respectively is

a) 0

b) 1

c) 10

d) 5

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8. Find the relative permittivity of the medium having a refractive index of 1.6

a) 0.4

b) 2.56

c) 3.2

d) 4.8

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^{2}= 1.62 = 2.56(no unit).

9. Calculate the transmission coefficient of a wave with a reflection coefficient of 0.6

a) 0.6

b) 1

c) 0

d) 0.4

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10.The phase constant of a wave propagation with frequency of 35 radian/sec and time delay of 7.5 sec is

a) 4.66

b) 262.5

c) 46.6

d) 26.25