Homework Help for Electrical Engineering

 A hydroelectric station has a turbine efficiency of 86% and a generator efficiency of 92%. The effective head of water is 150 m. Calculate the volume of water used when delivering a load of 40 Mw for 6 hours.

a. 74.18 x 104 m3

b. 4.158 x 104 m3

c. 82.54 x 103 m3

d. 94.48 x 104 m3

A diesel generator set burns diesel with a heating value of 18,000 BTU per lb. The diesel engine has an efficiency of 30% and the alternator has an efficiency of 95%. Determine the fuel cost component of producing one kW-hr if diesel cost P 2.8 per lb.

a. P 0.15

b. P 2.15

c. P 3.28

d. P 1.86

A power station has a load cycle as under

260 MW for 6 hrs  200 MW for 8 hrs 160 MW for 4 hrs  100 MW for 6 hrs

If the power station is equipped with 4 sets of 75 MW each, calculate the daily fuel requirement if the calorific value of the oil used were 10,000 Kcal/kg and the average heat rate of the station were 2,860 Kcal/kW.

a. 1890 tons

b. 3452 tons

c. 7641 tons

d. 1258.4 tons

Certain coal fired power plant has a heat rate of 2.88 x 108 calories per kW-hr. Coal costs P 2,500 per Ton. How much is the fuel cost component of producing 1 kW-hr?

a. P 2.50

b. P 1.00

c. P 1.75

d. P 1.25

A coal Thermal Power Plant has a boiler, turbine and alternator efficiencies of 35%, 86%, and 93% respectively. Coal with heating value of 12,000 BTU per lb cost P 1.5 per lb. What is the fuel cost in producing 1 kW?

a. P 1.9 per kW

b. P 1.52 per kW

c. P 1.75 per kW

d. P 1.62 per kW

A diversity factor of 2.5 gives a saving of _____ % in the generating equipment.

a. 60

b. 50

c. 40

d. 25

A Power Plant has a maximum demand of 15 MW. The annual load factor and capacity factor are 50% and 40%, respectively. Determine the reserve capacity of the plant.

a. 7350 kW

b. 5370 kW

c. 3750 kW

d. 3075 kW

 A 100 MW coal fired power plant has an average heat rate of 9,500 BTU/ kWh. The plant load factor is 75%; the heating value of coal is12,000 BTU/ lb. Calculate the amount of coal usage for one day.

a. 1.425 x 106 lbs.

b. 2.235 x 105 lbs.

c. 1.425 x 106 lbs.

d. 1.826 x 106 lbs.

A Diesel station supplies the following loads to various consumers:

Industrial consumer = 1500 kw   Commercial establishment = 750 kw

Domestic power = 100 kw    Domestic light = 450 kw

If the maximum demand on the station is 2500 kw and the number of kwh generated per year is 45 x 105, determine the diversity factor and load factor.

a. 1.12, 20.5%

b. .97, 31.2%

c. 1.53, 65.7%

d. 21.1, 50.2%

6. For the following circuit.

Write down the node voltage equations that solve for it when: The system frequency is 1 kHz. II = 2.5<0 A and I 2=1<0 A (<= angle) (2 pts)

5. The following circuit can be used as part of a loudspeaker crossover network. These networks can be pictured as frequency sensitive voltage dividers. This circuit allows low frequency tones to go into the low frequency transducer labeled here as "Loudspeaker", a.k.a. woofer. The crossover frequency is the frequency f at which the reactance magnitude XL. equals the woofer's resistance.

If the woofer resistance is: R = 4 and L=1 mH.

5. The following circuit can be used as part of a loudspeaker crossover network. These networks can be pictured as frequency sensitive voltage dividers. This circuit allows low frequency tones to go into the low frequency transducer labeled here as "Loudspeaker", a.k.a. woofer. The crossover frequency is the frequency f at which the reactance magnitude equals the woofer's resistance.

5b) Find P F, S, and Q at 2000 Hz for an harmonic wave (i.e. sinusoidal signal) with a peak amplitude of 1V.

Consider the following voltage divider circuit: 

Identify the circuit as either a high pass filter, low pass filter, band pass filter, band stop filter or none of the above. 

The circuit above, is known to exhibit a resonance at a frequency given by ω02=1/LC. Show that the 3dB bandwidth of the circuit around this resonance is given by δω3dB=R/L. 

I understand that this is a complex question, however, I am stumped. Please help! Thank you!

Problem 4: Let's build a simplified model of the fields inside a resistor. Imagine you have a perfectly cylindrical resistor of length \ell and radius a, carrying total current I. If the total resistance is R, then there is a voltage drop V=I R down the length of the resistor. This means that the resistor contains an electric field inside it. What is the magnitude || and direction of that field E ? Give your answer in terms of R, , a, I.

Now that field must be created by charges; where are those charges? What charge densities must exist in this problem, and where? Imagine that the ends of the resistor are conducting circular plates of radius a and the

interior of the resistor is some kind of resistive material. Does it make sense now that any resistor must also have capacitance? Roughly how much charge +Q,-Q must be on those plates? Give your answer in terms of R, , a, I.

In order to solve this problem, assume that the field is entirely contained inside the resistor. That's not true! But this problem is intended to be conceptual not exact.

 

Now imagine (incorrectly, it also turns out) that the current is uniformly distributed throughout the resistor. What is the current density inside the resistor (magnitude and direction). You might have to look up the definition of current density in your textbook. The resistivity \rho we encountered in a previous Problem Set should be related to these by = \rho  . This is the "differential form" of Ohm's Law. Check that this works out in terms of units.

 

Now, finally, what is the direction and magnitude of the magnetic field at the surface of the resistor? Compute the "Poynting vector" quantity  

 

 

 

at the surface of the resistor. Integrate the flux of into the resistor by the standard way we do integrals of vectors over the surface of the resistor. Compare this integral to the power R dissipated by the resistor. Are the units the same? Is the value the same?