Electrical Engineering Answers

Unless stated otherwise, use 344 m/s for the speed of sound in air.

1. An astronaut visiting another planet measures the speed of sound in that atmosphere to be 950 m/s. She measures the density of the atmosphere to be 3.10 kg/m3.
a)What is the bulk modulus of this atmosphere?
b)What is the frequency of the 5th harmonic for an organ pipe of length L = 0.750 m open at both ends on this planet?
c)Suppose the astronaut now uses her hand to close one end of the pipe. What is the new length of pipe that would be needed to produce a 5th harmonic with the same frequency as you found in b)?

A mild steel ring has a mean circumference of 500 mm
and a uniform cross-sectional area of 300 mm2
.
Calculate the m.m.f. required to produce a flux of
500 µWb. An airgap, 1.0 mm in length, is now cut in
the ring. Determine the flux produced if the m.m.f.
remains constant. Assume the relative permeability
of the mild steel to remain constant at 220.

What is the most common method of con- trolling the speed of an alternating-current motor?

Design an XNOR gate with two inputs A and B using only NAND gates .Mention the expression in terms of A and B at the output of each NAND gate in your circuit diagram.

Design and draw voltage regulator to provide 4 to 10 volt variable output voltage using IC 7812.

Draw the output waveform indicating proper scales on the time and voltage axes for
the given input waveform (Vi) to the circuit shown in Fig. 2.

Write the following Boolean function in sum of products form: f = (b + d)(a’ + b’ + c)

1. A wave on a string has the form y(x,t)=−20 cos(3(pi)x - 12(pi)t + pi/6), with all values in SI units. a)Find its amplitude, (linear) frequency, wavelength, speed of propagation, direction of travel, maximum transverse speed and maximum transverse acceleration of the string. (Clearly label each of these answers and express in the appropriate units.)
b)Write the equation of another wave which if added to this one will produce a standing wave pattern. c)Provide the equation of the resulting standing wave.

2. In each case below, state whether the function represents a traveling wave or not:
a) y(x,t)=3cos[pi((x/2)-t)]
b) y(x,t)=3cos[pi((x/2)-t)]sin[pi((x/2)+t)]
c) y(x,t)=3cos[pi((x/2)-t)]sin[pi(x-2t)]
d) y(x,t)=3sin[pi((x/2)-t)]sin[pi(2x-t+4)]
e) y(x,t)=3e^−(3x+2t)

1. A transverse wave on a taut string is given by
y(x, t)=(0. 750 cm)cos[pi{(0.400 rad/cm)x + (250rad/s)t}]
[Note the 휋휋 inside the cosine function!!!]
a) What is the amplitude?
b) What is the period?
c) What is the (linear) frequency?
d) What is the wavelength?
e) What is the speed of propagation?
f) What is the direction of propagation (+x-direction or –x-direction)?
g) If the mass per unit length is 50.0 g/m, what is the tension in the string in newtons?
h) What is the displacement of a point on the rope located at x = 56.4 cm at time t = 0.115 s?

9)Draw a hazard free AND‐OR circuit for the K‐MAP below and then draw a hazard free OR‐AND circuit. Remember a SOP equation is created by circling the ones and generates an AND‐OR circuit. A POS equation is created by circling the zeros and generates an OR‐AND circuit. ሺ0,4,5,7,8,9,10,11,12,13,15ሻ݉෍ ൌ ܨ10)Repeat the previous problem but do not add the group making the AND‐OR circuit hazard free. a.What is the expected output when A=1,B=1,C=0 and D=1? b. What is the expected output when A=1,B=1,C=0 and D=0?c. Assume A=1,B=1 and C=0. Create a timing diagram that shows a glitch (momentary 0) occurring on the output when D changes from 1 to 0. Assume all gates have a 5ns propagation delay.