# Multiple choice question for engineering

## Set 1

1. The loss tangent refers to the

a) Power due to propagation in conductor to that in dielectric

b) Power loss

c) Current loss

d) Charge loss

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2. Calculate the conduction current density when the resistivity of a material with an electric field of 5 units is 4.5 units.

a) 22.5

b) 4.5/5

c) 5/4.5

d) 9.5

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3. At high frequencies, which parameter is significant?

a) Conduction current

b) Displacement current

c) Attenuation constant

d) Phase constant

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4. Find the loss tangent of a material with conduction current density of 5 units and displacement current density of 10 units.

a) 2

b) 0.5

c) 5

d) 10

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5. The loss tangent is also referred to as

a) Attenuation

b) Propagation

c) Dissipation factor

d) Polarization

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6. The loss tangent of a wave propagation with an intrinsic angle of 20 degree is

a) Tan 20

b) Tan 40

c) Tan 60

d) Tan 80

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7. The expression for the loss tangent is given by

a) σ/ωε

b) ωε/σ

c) σ/ω

d) ω/ε

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8. Find the loss angle in degrees when the loss tangent is 1.

a) 0

b) 30

c) 45

d) 90

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^{-1}(1) = 450.

9. The complex permittivity is given by 2-j. Find the loss tangent.

a) 1/2

b) -1/2

c) 2

d) -2

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10. The intrinsic angle of the wave with a loss angle of 60 is

a) 120

b) 60

c) 90

d) 30

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## Set 2

1. The transmission line is said to be lossless when the

a) Conductor is perfect and dielectric is lossless

b) Conductor is perfect and dielectric is lossy

c) Conductor is imperfect and dielectric is lossy

d) Conductor is imperfect and dielectric is lossless

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2. The resistance of a lossless transmission line is

a) 0

b) 1

c) -1

d) Infinity

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3. Which two parameters given below are zero in the lossless line?

a) L, C

b) C, G

c) G, α

d) R, L

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4. The characteristic impedance of the line having primary constants L and C as 35 milli henry and 70 micro farad respectively is

a) 500

b) 22.36

c) 125

d) 50

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^{-3}and C = 70 x 10

^{-6}, we get Zo = √(500) = 22. 36 ohm.

5. The attenuation constant is measured in the units of

a) Ohm

b) Neper

c) Decibel

d) Radian/sec

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6. The velocity of the transmission line with a frequency of 35 radian/s and phase constant of 68.5 is

a) 1.95

b) 2.36

c) 4.56

d) 3.48

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7. The condition that holds good in a distortionless transmission line is

a) R/L = G/C

b) RL = GC

c) L/R = C/G

d) RG/LC

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8. Given that R = 20 ohm, L = 40 mH, C = 40 μF, G = 0.02 mho. Find whether the line is distortionless or not.

a) Distorted line

b) Distortionless line

c) All of the mentioned

d) None of the mentioned

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9. For R= 20 ohm and G= 0.8 mho, the attenuation constant will be

a) 16

b) 4

c) 2

d) 32

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10. The velocity of an electromagnetic wave with frequency 6MHz and a skin depth of 1.6 μm.

a) 3.75

b) 0.26

c) 9.6

d) 7.8

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^{6}and δ = 1.6 x 10

^{-6}, we get v = 6 x 10

^{6}x 1.6 x 10

^{-6}= 9.6 units.

11. The characteristic impedance of the transmission line with R= 45 ohm and G= 0.45 mho is

a) 100

b) 1

c) 0.1

d) 10

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12. The distortionless line is one in which the attenuation constant and phase constant are independent of the frequency. State true/false.

a) True

b) False

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## Set 3

1. The magnetic moment of a field with current 12A and area 1.6 units is

a) 19.2

b) 12.9

c) 21.9

d) 91.2

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2. Find the torque of a loop with magnetic moment 12.5 and magnetic flux density 7.65 units is

a) 95.625

b) 65.925

c) 56.525

d) 65.235

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3. The magnetization is defined by the ratio of

a) Magnetic moment to area

b) Magnetic moment to volume

c) Magnetic flux density to area

d) Magnetic flux density to volume

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4. Find the orbital dipole moment in a field of dipoles of radius 20cm and angular velocity of 2m/s(in 10^{-22} order)

a) 64

b) 76

c) 54

d) 78

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^{2}, where e = 1.6 x 10

^{-19}is the charge of the electron, Vang = 2 and r = 0.2. On substituting, we get M = 0.5 x 1.6 x 10

^{-19}x 2 x 0.2

^{2}= 64 x 10

^{-22}units.

5. Find the orbital angular moment of a dipole with angular velocity of 1.6m/s and radius 35cm(in 10-31 order)

a) 1.78

b) 8.71

c) 7.18

d) 2.43

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^{2},where m = 9.1 x 10

^{-31}, Vang = 1.6 and r = 0.35. On substituting, we get, Ma = 9.1 x 10

^{-31}x 1.6 x 0.35

^{2}= 1.78 x 10

^{-31}units.

6. The ratio of the orbital dipole moment to the orbital angular moment is given by

a) e/m

b) –e/m

c) e/2m

d) –e/2m

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^{2}and the orbital angular moment is given by Ma = m x Vangx r

^{2}. Their ratio M/Ma is given by –e/2m, the negative sign indicates the charge of electron.

7. Calculate the Larmer angular frequency for a magnetic flux density of 12.34 x 10^{-10}.

a) 108.36

b) 810.63

c) 368.81

d) 183.36

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^{-10}x 1.6 x 10

^{-19}/(2 x 9.1 x 10

^{-31}) = 108.36 units.

8. The Bohr magneton is given by

a) eh/2m

b) eh/2πm

c) eh/4m

d) eh/4πm

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9. Find the magnetization of the field which has a magnetic moment 16 units in a volume of 1.2 units.

a) 16.67

b) 13.33

c) 15.56

d) 18.87

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10. Which of the following is true regarding magnetic lines of force?

a) Real

b) Imaginary

c) Does not exist

d) Parallel to field

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## Set 4

1. Identify which of the following is the unit of magnetic flux density?

a) Weber

b) Weber/m

c) Tesla

d) Weber^{-1}

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^{2}. It is also called as tesla.

2. The divergence of H will be

a) 1

b) -1

c) ∞

d) 0

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3. Find the flux contained by the material when the flux density is 11.7 Tesla and the area is 2 units.

a) 23.4

b) 12.3

c) 32.4

d) 21.3

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4. Find the current when the magnetic field intensity is given by 2L and L varies as 0->1.

a) 2

b) 1

c) 0.5

d) 0

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5. Find the magnetic field intensity when the flux density is 8 x 10^{-6} Tesla in the medium of air.

a) 6.36

b) 3.66

c) 6.63

d) 3.36

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^{-6}and μ = 4π x 10

^{-7}. Thus H = 8 x 10

^{-6}/ 4π x 10

^{-7}= 6.36 units.

6. If ∫ H.dL = 0, then which statement will be true?

a) E = -Grad(V)

b) B = -Grad(D)

c) H = -Grad(Vm)

d) D = -Grad(A)

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7. Find the magnetic flux density of the material with magnetic vector potential A = y i + z j + x k.

a) i + j + k

b) –i – j – k

c) –i-j

d) –i-k

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8. Find the magnetic flux density when a flux of 28 units is enclosed in an area of 15cm.

a) 178.33

b) 186.67

c) 192.67

d) 124.33

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9. Find the magnetic flux density B when E is given by 3sin y i + 4cos z j + ex k.

a) ∫(4sin z i – ex j – 3cos y k)dt

b) -∫(4sin z i – ex j – 3cos y k)dt

c) ∫(4sin y i – ex j + 3cos y k)dt

d) -∫(4sin y i + ex j + 3cos y k)dt

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10. Find current density J when B = 50 x 10-6 units and area dS is 4 units.

a) 9.94

b) 8.97

c) 7.92

d) 10.21

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^{-6}/ 4π x 10

^{-7}= 39.78 units. Also H = ∫ J.dS, where H = 39.78 and ∫ dS = 4. Thus J = 39.78/4 = 9.94 units.

## Set 5

1. The H quantity is analogous to which component in the following?

a) B

b) D

c) E

d) V

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2. The magnetic flux density is directly proportional to the magnetic field intensity. State True/False.

a) True

b) False

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3. Ampere law states that,

a) Divergence of H is same as the flux

b) Curl of D is same as the current

c) Divergence of E is zero

d) Curl of H is same as the current density

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4. Given the magnetic field is 2.4 units. Find the flux density in air(in 10^{-6} order).

a) 2

b) 3

c) 4

d) 5

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^{-7}and H = 2.4, we get B = 4π x 10

^{-7}x 2.4 = 3 x 10

^{-6}units.

5. Find the electric field when the magnetic field is given by 2sin t in air.

a) 8π x 10^{-7} cos t

b) 4π x 10^{-7} sin t

c) -8π x 10^{-7} cos t

d) -4π x 10^{-7} sin t

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^{-7}x 2sin t = 8πx10

^{-7}sin t. To get E, integrate B with respect to time, we get 8πx10

^{-7}cos t.

6. Find the height of an infinitely long conductor from point P which is carrying current of 6.28A and field intensity is 0.5 units.

a) 0.5

b) 2

c) 6.28

d) 1

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7. Find the magnetic field intensity due to a solenoid of length 12cm having 30 turns and current of 1.5A.

a) 250

b) 325

c) 175

d) 375

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8. Find the magnetic field intensity at the radius of 6cm of a coaxial cable with inner and outer radii are 1.5cm and 4cm respectively. The current flowing is 2A.

a) 2.73

b) 3.5

c) 0

d) 1.25

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9. Find the magnetic field intensity of a toroid of turns 40 and radius 20cm. The current carried by the toroid be 3.25A.

a) 103.45

b) 102

c) 105.7

d) 171

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10. The magnetic field intensity of an infinite sheet of charge with charge density 36.5 units in air will be

a) 18.25

b) 11.25

c) 73

d) 1/36.5