Electrical Engineering Answers

The impulse response of a discrete-time LTI system is
h(n) = 2δ(n) − δ(n − 4).
Find and sketch the output of this system when the input is the step function
x(n) = u(n).

The impulse response of a discrete-time LTI system is
h(n) = δ(n) + 2δ(n − 1) + δ(n − 2).
Sketch the output of this system when the input is
............∞
x(n) =∑δ(n − 4 k).
...........k=0

The equation for the instantaneous voltage across a discharging capacitor is given by, where is the initial voltage and is the time constant of the circuit


The tasks are to:


A) draw a graph of voltage against time for and, between and.

B) calculate the gradient at and

C) differentiate and calculate the value of at and

D) compare your answers with part b and part c

E) calculate the second derivative of the instantaneous voltage

What are main factors affecting choice of connections in three phase transformers? Mention
any five.

Two electric furnaces are supplied with 1- phase current at 80V from a three phase,11 KV
system by means of two single-phase Scott connected transformers with similar secondary
windings. When load on one furnace is 0.5 MW (teaser secondary) and on other furnace is 0.8
MW (Main transformer secondary).
What current will flow in each of three phase lines at
i) Unity power factor
ii) 0.5 power factor

A ladder 15ft long rest against a vertical wall. Its top slides down the wall while its bottom moves away along with the level ground at a speed of 2 ft/s . How fast is the angle between the top of the ladder and the wall changing when the angle is π/3 radians.

A plate previously cold worked at 45% is 50mm thick.Its is then cold worked further by 27mm. What is the percentage cold work?

Design an arbitrary counter which generates multiples of 3 at the output. But, the output is never greater than 30. Further, two successive outputs are always greater than 5. First, draw state diagram, write all the design steps and draw the final circuit.

If v(t) = 10 cos(120πt+30o
) and i(t) = 6 cos(120πt+60o
), determine the average power, rms value of v(t),
and the power factor