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# Monthly Archives: January 2017

## Electromagnetic Waves GATE Questions and Answers

1.  A plane electromagnetic wave travelling along +z direction, it has its electric field given by

$E_x$= 2 $cos(\omega t)$  and

$E_y$= 2 $cos(\omega t+90)$

the wave is

a) Linearly polarized

b) Elliptically polarized

c) Left circularly polarized

d) Right circularly polarized

2) The electric field of an electromagnetic wave propagating in the positive z direction is

$E$ =$i sin( \omega t$$\beta z)$$i sin( \omega t$$\beta z +90)$ The wave is

a) Linearly polarized in the Z direction

b) Elliptically polarized

c) Left Hand circularly polarized

d) Right Hand circularly polarized

3) The electric field of a uniform plane electromagnetic wave in free space, along the positive x direction, is given by

E =$10(a_y +j a_z)$ $e^{-j25x}$

The frequency and polarization of the wave are

a) 1.2 GHz and left circular
b) 4 GHz and left circular
c) 1.2 GHz and right circular
d) 4 GHz and right circular

4) A plane wave propagating in the dielectric medium has an electric field given as
Ex  = E0Cos (2.6×1010t -100z). The phase velocity of plane wave is:

a) $10^6 m/s$

b) $2.6*10^8 m/s$

c) $3*10^8 m/s$

d) $2.6*10^{12} m/s$

## What is magnetic field intensity at centre of current carrying loop(Circle)

1) B= $\frac{\mu_oI}{4r}$

2) B= $\frac{\mu_oI}{2r}$

3) B= $\frac{\mu_oI}{2 \pi r}$

4) B= $\frac{\mu_oI}{4 \pi r}$

## GATE Communication system MCQ’s

1) The convergence of Fourier transform is

a) along jw axis in s-plane
b) on a rectangular strip in s-plane
c) along a circle in s-plane
d) on a circular strip in s-plane

2) Convolution of two voltage pulses of amplitude 2 Volt and width 2 sec is a

a) Rectangular pulse
b) square pulse
c) Trapezoidal
d) Triangular pulse

3) The FT of v(t) is $e^{-j2w}$ for |w|<=1. The Energy dissipated by 1 $\Omega$ resistor, if v(t) is applied to it is

a) 1/$\pi$
b) 2/$\pi$
c) $e^{-j2}/\pi$
d) $e^{-2}$

4) $\delta(2t)$ equals

a)2 $\delta(t)$
b) 2 u(t)
c) $\delta(t)$
d) 0.5 $\delta(t)$

5) A box contains 12 balls numbered from 1 to 12. If a ball is taken at random, what is the probability of getting a ball with a number which is a multiple of either 2 or 3.

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6) A box contains 2000 transistors of which 5 % are defective. A second box contains 500 transistors of which 40% are defective. Two other boxes contain 1000 transistors of which 10% are defective transistors. A single transistor is taken at random from one of the boxes.
i) What is the probability that selected transistor is defective?
ii) What is the probability that defective transistor is taken from box 2?

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