ENGR 111 Exam 3 ReviewDec. 1, Thu., 8:15-9:45pm

Zachry 102

Closed book, closed notes.

No calculators allowed. No teaming.

Scantrons will be provided.

Leave belongings (cell phones, backpacks, etc.) by the stage in front of the class.

Topics (Covered in Exam 1)

Engineering, Engineering DesignDC Basics

KCL, KVL, Ohm’s Law, power, energy, current and voltage dividers, resistors in series and parallel

AC BasicsCapacitance, inductance, transformers, RC circuits

Semiconductors, Transistors

Topics (Covered in Exam 2)

Binary, Logic, Memory ElementsBinary representation, Gates, Truth tables, Logic rules,

SR Latches, SRAM/DRAM

Computer systems, MemoryDigital information, Transmission, Spectrum,

ModulationASCII, images, audio/video, Sampling theorem, Delay,

Noise, SNR, Digital vs. analog, AM/FM, Modems, Spectrum sharing

True/False Review

The sum of currents flowing into a node in a circuit depends on the voltage applied to the circuit components.

The power dissipated by a resistor is lower for a 100. V AC source as compared to a 100. V DC source.

The ratio of voltages across two resistors connected in parallel depends on the values of the two resistors.

A transformer can be used to convert a 120 V AC source to a 12 V DC source.

The power dissipated in an ideal inductor is zero.

KCL, KVL

Given: Va=10.0 v, Vb=5.0 v, Vc=10.0 v; R1=10.0 k, R2=5.0 k

I1=(Va-Vb)/R1=(10.0-5.0)/10.0k=0.50 mAI2 =(Vb-Vc)/R2=(5.0-10.0)/5.0k=1.0 mAI3 = I1+I2= 1.5 mAVAB=VaVb=5.0 v, VBC=VbVc=5.0 v, VAC=VaVc=0

Resistors in Series and Parallel

Which one of the resistors dissipates the maximum power in these circuits? R1=10.0 , R2=20.0 , R3=30.0 .

V

R1 R2 R3

V

R1

R2

R3

Voltage Dividers

What is Vout? What if load is applied?

R

Vin

(B)

Vout

R

Vin

(A)

VoutR

R

AC

The maximum voltage across a light bulb connected to a 120. V AC outlet is …

Power consumed in the circuit is …

V

R1 R2

AC

RC CircuitsVs = 27.18 v,

R=10.0 k, C=100. F

Thus, RC = 1.00 s

Switch closed at t=0.0 s

Vc=0.0 V at t=0.0

Time Current through R

Right after switch is closed Vs/R=2.72 mA

t=1.0 s Vs/R * 1/e = 1.00 mA

t=2.0 s Vs/R * 1/e2 = 1.00/e mA

t=20.0 s Vs/R * 1/e20 = 0 mA

Digital Information

In full HD mode, your 1080p TV displays video at 30 frames/second, with each frame being 1920x1080 pixels, where each pixel is represented by 3 colors, each of 8 bits. How many seconds of uncompressed full HD video can a 50 GB Blu-Ray disk hold?

50109

192010803038 50109/(192010803038) 50109/(19201080303) None of the above

Transmission

Which if these are true for digital signal transmission?

Allows accurate reconstruction of signal even in the presence of noise

Eliminates attenuation Is less efficient than analog transmission Requires repeaters or regenerators to

transmit over long distances

Sampling

At what rate should a 25 kHz signal be sampled to allow perfect reconstruction?

12,500 samples per second 25,000 samples per second 50,000 samples per second 25,000/sqrt(2) samples per second None of the above

Communication

How much time does it take to download a 1 Mb file over a 1000 km long, 100 Mbps fiber optic cable? (Assume speed of light in fiber is 2x108 m/s.)

100 ms 50 ms 15 ms (tprop = 5 ms; L/R= 10 ms) 5 ms

Compression

The size of 16 minute video compressed to 1 Mbps is

16x106 bits 128x106 bytes 120x106 bytes 960x106 bytes