Electrical Engineering Answers

Suppose that we have a Calling Center in which a random caller (discrete random variable) Xd
with (generalized) PDF and CDF fd(x) and Fd(x), and a continuous random variable Xc with
PDF and CDF fc(x) and Fc(x). Now we create a new Calling System with random variable X in
the following way. We have a caller with P(H)=p. if a call connects, then the value of X is
determined according to the probability distribution of Xd. If the call does not connects, the
value of X is determined according to the probability distribution of Xc
a. Find the CDF of X, F(x).

b. Find the PDF of X, f(x).
c. Find E(X). & Var(X)

In a communication system, packets are transmitted from a sender to a receiver. Each
packet is received with no error with probability p independently from other packets
(with probability 1−p the packet is lost). The receiver can decode the message as soon as
it receives k packets with no error. Compute the probability that the sender sends exactly
n packets until the receiver can decode the message successfully

[1] A modern petroleum refinery will contain a distillation tower, a catalytic cracking tower (referred to as a cat cracker), a catalytic reforming unit (also called a cat reformer), a polymerization unit, and an isomerization unit, among other units. State the principal end objective or purpose of each of these towers or units. State also the activity carried out in the unit in order to achieve its objective.
[2] Give a brief description of main types of coal pyrolysis technologies and their characteristics. (you can describe it from the point of view of reactor, process, or temperature, etc.)
[3] Give a brief description of biomass gasification and main related chemical processes including gasification applications.
[4] Write the correct cathode half reactions of AFC, PAFC, MCFC, PEMFC and SOFC.

2mWb is to be produced in the air gap of the magnetic circuit shown in figure 21.17. How much ampere turns the coil must provide to achieve this? Relaqtive permeability ?r of the core material may be assumed to be constant and equal to 5000. All the dimensions shown are in cm and the sectional area is 25cm2 throughout.

A current transformer has a single turn on the primary winding and a secondary winding of 60 turns. The secondary
winding is connected to an ammeter with a resistance of 0.15Ω. The resistance of the secondary winding is 0.25Ω. If
the current in the primary winding is 300 A, determine (a) the reading on the ammeter, (b) the potential difference
across the ammeter and (c) the total load (in VA) on the secondary.

An air-gap between two pole pieces is 20 mm in length and the area of the flux path across the gap is 5 cm2. If the flux required in the air-gap is 0.75 mWb. Find the mmf necessary.

A steel ring has a mean diameter of 15 cm, a cross-section of 20 cm2
and a radial airgap of 0.5
mm cut in it. The ring is uniformly wound with 1500 turns of insulated wire and a magnetizing
current of 1 A produces a flux of 1 mWb in the airgap. Neglecting the effect of magnetic leakage
and fringing, calculate: (a) the reluctance of the magnetic circuit; (b) the relative permeability
of the steel.

A shunt dc motor has the following specifications; field resistance of 170 ohm armature resistance of 3 ohm, armature current of 7A, voltage source of 14V and flux density of 5Vs determine the; rated torque, starting torque, starting current at full voltage, starting speed, speed at the rated torque.

A shunt dc motor has the following specifications; field resistance of 170 ohm, armature resistance of 3 ohm, armature current of 7A, voltage source of 14V and flux density of 5Vs determine the; rated torque, starting torque, starting current at full voltage, starting speed, speed at the rated torque.

calculate the dynamic slope resistance when a voltage of 50V is applied across a germanium diode at 300K when saturation current is 10uA