Electrical Engineering Answers

A parallel plate capacitor has its plates separated with a slab of 4mm thickness and a dielectric

constant of 3. If the capacitance is to be one-third of the original value when a second slab of

6mm thickness is inserted between the plates, what should be the relative permittivity of the

second slab?

Draw the phasor diagram representing the five electromotive forces

e1= 20 sinwt

e2= 10 sin ( wt+pi/3)

e3=15 coswt

e4=10 sin ( wt-pi/3)

e5=25 cos (wt+2pi/3) and their resultant.

Express the resultant voltage in the form e sin (wt+fi).

A voltage source 𝑣(𝑡) = 240 sin(314.16𝑡 − 20°)𝑉 is connected to a load having an

impedance of Z. The resulting current through the load is 𝑖(𝑡) = 15 sin(314.16𝑡 + 22.5°)A.

Determine the circuit power factor and identify the elements that constitute the load, given

that Z comprises of only two elements connected in series.

Design an operational amplifier circuit to form the weighted sum V0 = – (2V1+V2).

A 10mV, 2KHz sinusoidal signal is applied to the input of an op-amp integrator for which R=100 kΩ and C=1 μF. Find the output voltage.

A 228V constant potential generator delivers load to a variable impedance whose values of R and X 

are readily adjustable. Assuming a looking-back impedance of (6+j4.5) ohms calculate, for maximum 

power,

a. The load impedance

b. The current

c. Load power

d. power factor

Slove this question according to figure 04.

1. Find the Thevenin equivalent circuit looking from the terminals a-b as shown in Figure 04.
2. In Figure 04, assume that the load is purely resistive (RL), determine the value of the load resistor RL across terminals a-b for maximum average-power transfer, and calculate the RMS value of the load current when RL is connected between terminals a-b.
3.  Calculate the complex power drawn by the load when RL is connected between terminals a-b.

Task 1:

Prepare and deliver a presentation on two applications using electrical energy chosen from the list below:

• intelligent street lighting systems,

• automated processes and robotics in manufacturing,

• automated rail transport systems,

• electric cars

• solar powered space travel

Your presentation should include an explanation (in terms of electrical or electronic principles) how they use two of the following:

• Electromagnetic effects

• Sensors (photodiode, LED, position detectors, Hall effect, etc.)

• Computer control (including PLA (programmable logic arrays)

• Battery technologies

Task 2

Explain and justify how the existing technology can be used to improve one of the systems you chose for Task 1. Specify in terms of electrical principles, how you suggested improvement work.

Make a detailed explanation of why a range of voltages is used such as 15 to 25kV at the generators and up to 400kV for transmission, and the reasons for other voltages (e.g. 33kV and 11kV down to 400/230 volts) for light industrial and domestic end users.

A: With the aid of a suitable diagram, describe the generation of electrical energy in a power station

B: With the aid of a suitable diagram, describe the transmission and distribution of electricitythrough to the end users

C: With the aid of a suitable diagram/sketch briefly describe the types of transformers used.Include double wound, autotransformers and isolating transformers