Radar has a power of 1 kW and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance up to which it can detect objects located on the surface of the earth (Radius of earth = 6.4 x 106m) is 1) 80 km 2) 16 km 3) 40 km 4) 64 km Answer: 1) 80 km Solution: Let d be the maximum distance at which the object can be detected... View Article
Phase difference between space current and capacitive current is 1) π rad 2) π/2 rad 3) 3π/2 rad 4) μ rad Answer: 1) π rad Solution: The phase difference between space current and... View Article
What is the velocity of electromagnetic waves in a good conductor 1) 3 x 108 m/s 2) More than 3 x 108 m/s 3) High 4) Very low Answer:Â 4) Very low Solution: The velocity of electromagnetic waves in a... View Article
How long will it take to transmit the information 30 km away in space? 1) 0.1 m s 2) 0.1 µ s 3) 0.1 n s 4) 0.1 p s Answer: 1) 0.1 m s Solution: Velocity of light in space,= [(distance... View Article
When electromagnetic waves enter the ionised layer of the ionosphere, the relative permitting of the ionised layer 1) Remain constant 2) Appears to decrease 3) Appears to increase 4) Changer randomly Answers: 2) Appears to decrease Solution:... View Article
For 100% modulation, What is the value of minimum amplitude ( Emin ) of the modulated wave? 1) Zero 2) 1 3) 2 4) 3 Answer: 1) Zero Solution: m = [(Emax – Emin) / (Emax + Emin)] × 100 For m = 100%, Emin should be zero.... View Article
A silicon optical fibre with a core diameter large enough has a care refractive index of 1.50 and a cladding refractive index of 1.47. The critical angle at the core-cladding interface is ___________ 1) 87.50 2) 78.50 3) 38.50 4) 450 Answer: n1 = core refractive index = 1.5 n2 = cladding refractive index = 1.47 Critical angle θ = sin–1... View Article
What type of medium is used in optical communication? 1) Guided medium 2) Unguided medium 3) Both guided and unguided media 4) Neither guided nor unguided media Answer: 1) Guided medium... View Article
What is the frequency range of signals that can be transmitted in the care of twisted pair of wires? 1) 5 MHz to 20 MHz 2) 5 MHz to 10 MHz 3) 100 Hz to 4 MHz 4) 5 MHz to 20 MHz Answer: 3) 100 Hz to 4 MHz Solution: The frequency... View Article
A T.V. tower has a height of 200 m. By how much the height of the tower is increased to triple its coverage range? 1) 1600 m 2) 800 m 3) 1800 m 4) 600 m Answer: 1) 1600 m Solution: Here, h=200m,as d=√2hr and d'=√2h'R d'=3d... View Article
In order to cover a circular region of radius 128 km by a TV transmitter, what must be the height of the transmitting antenna? 1) 79 m 2) 1050 m 3) 1280 m 4) 1560 m Answer: 3) 1280 m Solution: Area of circular region = πR2 = 3.14 × (128)2 =... View Article
A rod AB of length 16 cm rests between the wall AD and a smooth peg, 1 cm from the wall, and makes an angle θ with the horizontal. The value of θ for which the height of G, the midpoint of the rod above the peg is minimum, is (a) 150 (b) 300 (c) 600 (d) 750 Solution: We have AC = sec θ, AG = 8 CG = 8 - sec θ (C being the peg). u = CG sin θ = (8 - sec θ) sin θ... View Article
The difference between greatest and least value of f(x) = 2 sin x + sin 2x, x ∈ [0, 3Ï€/2] is (a) 3√3/2 (b) 3√3/2 - 2 (c) (3√3/2) + 2 (d) none of these Solution: f(x) = 2 sin x + sin 2x Differentiate w.r.t.x... View Article
If OT is the perpendicular drawn from the origin to the tangent at any point t to the curve x = a cos3 t, y = a sin3 t, then OT is equal to (a) a sin 2t (b) (a/2) sin 2t (c) 2a sin 2t (d) 2a Solution: Given x = a cos3 t y = a sin3 t dx/dt = -3a cos2t sin t dy/dt... View Article
The fuel charges for running a train are proportional to the square of the speed generated in miles per hour and costs Rs. 48 per hour at 16 miles per hour. The most economical speed if the fixed charges i.e. salaries etc. amount to Rs. 300 per hour is (a) 10 (b) 20 (c) 30 (d) 40 Solution: Let the speed of the train be v and distance to be covered be s so that the... View Article
The profit function, in rupees, of a firm selling x items (x≥ 0) per week is given by P(x) = – 3500 + (400 – x)x. How many items should the firm sell so that the firm has maximum profit? (a) 400 (b) 300 (c) 200 (d) 100 Solution: Given P(x) = - 3500 + (400 - x)x = -3500 + 400x - x2 Differentiate... View Article
If f(x) = x ln x, then f(x) attains minimum value at which one of the following points? (a) x = e–2 (b) x = e (c) x = e–1 (d) x = 2e–1 Solution: Given f(x) = x ln x Differentiate w.r.t.x... View Article
Area of the triangle formed by the normal to the curve x = esin y at (1, 0) with the coordinate axes is : (a) 1/4 (b) 1/2 (c) 3/4 (d) 1 Solution: Given x = esin y Take log on both sides log x = sin y log e log x = sin... View Article
If the function y = (ax+b)/(x-1)(x-4) has turning point at P(2, -1), then (a) a = b = 1 (b) a = b = 0 (c) a = 1, b = 0 (d) a = b = 2 Solution: Given y = (ax+b)/(x-1)(x-4) has turning point at P(2,... View Article
A curve is represented by the equation x = sec2t and y = cot t, where t is a parameter. If the tangent at the point P on the curve where t = π/4 meets the curve again at the point Q, then |PQ| is equal to (a) 5√3/2 (b) 5√5/2 (c) 2√5/3 (d) 3√5/2 Solution: Given x = sec2t y = cot t dx/dt = 2 sec t sec t tan... View Article
