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Homework 4 Answers - Homework 4 Answers Back You are...

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Homework 4 Answers Back You are encouraged to run PSpice and look at web sites during this homework quiz. The questions review some things you should have learned in experiment 4 and help prepare you for experiment 5. Question 1 (1 point) Question 4-1 In this bridge circuit, the value of R1 is 1K ohms, the value of R2 is 1K ohms, the value of R3 is 1K ohms, and the value of R4 is 950 ohms , find the peak voltage difference between the two points (Vleft - Vright), when the VSIN source has a maximum voltage of 200 millivolts, a frequency of 2K Hertz (cycles/sec) and no DC offset. Express your answer in millivolts. Note that this voltage has a sign.

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Student response: 2.56 Correct answer: 2.56410 General feedback: We will use a bridge to find the value of a very small signal. When R1/R2 is not proportional to R3/R4, then the output of the bridge (Vleft-Vright) is a non-zero (positive or negative) value proportional to the difference in the resistances. When R1/R2 is equal to R3/R4, the bridge is balanced and the output (Vleft-Vright) should be zero. Score: 1 / 1 Question 2 (1 point) Question 4-2
In this bridge circuit, what is the value of R4 that balances the circuit, if R1 = 2K ohms, R2 = 3K ohms, R3 = 3K ohms, VSIN source has a maximum voltage of 300 millivolts, a frequency of 1K Hertz (cycles/sec) and no DC offset. Express your answer in K ohms. Student response: 4.5 Correct answer: 4.50000 General feedback: We will use a bridge to find the value of a very small signal. When R1/R2 is not proportional to R3/R4, then the output of the bridge (Vleft-Vright) is a non-zero (positive or negative) value proportional to the difference in the resistances. When R1/R2 is equal to R3/R4, the bridge is balanced and the output (Vleft-Vright) should be zero. Score: 1 / 1

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Question 3 (1 point) Question 4-3 In the bridge circuit below, which formula will give a correct value for R4 in terms of the voltage between Vleft and Vright (dV = Vleft- Vright), the resistance of R1, R2 and R3 (all equal to R) and the source voltage (V). Student response: Percent Value Correct Response Student Response Answer Choices 0.0% a. R4 = R * (V + dV) / V 100.0% b. R4 = R * (V - 2*dV) / (V + 2*dV)
0.0% c. R4 = R * (V + dV) / (V - dV) 0.0% d. R4 = R * (V - dV) / (V + dV) 0.0% e. R4 = R * (V - 2*dV) / V 0.0% f. R4 = R * (V + 2*dV) / V 0.0% g. R4 = R * (V - dV) / V General feedback: Write and expression for Vleft and Vright using the voltage divider rule. Set dv = (expression for Vleft)-(expression for Vright). Solve for R4. You may have to play with the equations to get the answer in the form listed. Score: 1 / 1 Question 4 (1 point) Question 4-4 In the following circuit, find the Thevenin voltage for a load placed between A and B when V1=14 volts, R1=3K ohms, R2=4K ohms, R3=3K and R4=2K ohms. Express your answer in volts.

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Student response: 5.6 Correct answer: 5.60000 General feedback: Thevenin voltage is found by removing the load (if there is one), and calculating the voltage across the load. (In this case, there is no load to remove and we are interested in the voltage from A to B). Note that if there is no current going through a resistor, it should be treated like a short with the same voltage at both ends.
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