PHYSICS 220BL #85094, #85512

FINAL EXAMINATION SPRING 2001

NAME___________

PART I (50%)

Answer the following questions: 

You must give a detailed answer.

  1. What is the difference between ammeter and galvanometer? How do you connect the ammeter in the circuit?
  2. How can you tell a battery is bad? How do you measure the emf and the internal resistance of a battery?
  3. What precautions do we take when we use Wheatstone Bridge? How can we get more precise measurement using Wheatstone-Bridge?
  4. We can measure a physical quantity through experiment, and calculate this quantity in an equation by using other physical quantities that are measured experimentally. Of the two results, which one do you trust better, experimental, or calculated? Reason your answer with an example and give a complete discussion.
  5. Is your result of “Charge-to-Mass-Ratio-of-Electron” satisfactory? Defend your answer.
  6. There is an inductor whose inductance is unknown. Can you tell its inductance using a varying frequency ac power supply, a resistor of resistance R, and a capacitor of capacitance C? Give the relevant equations.
  7. What is the advantage of oscilloscope over the ac voltmeter? Give an example to support your statement.
  8. What precaution do we have to take when we construct a step-up transformer? A transformer’s primary voltage is 120V, and the secondary current is 1A. Assume that the transformer is an ideal transformer with output of 12W, that is, no energy loss.  What is the primary- to- secondary-ratio? Is it a step-up or step-down transformer?
  9. Did you ever notice the difference between the equipotential lines in the middle of the black paper and the lines at the both ends of the paper? State the reason why they have the difference.
  10. What is the most vulnerable part of the digital multi-meter? How do you pay attention to using the multi-meter?

 

PART II (50%)

Virtual experiment: There are a few unknown capacitors. Design a procedure to find their capacitances. You need to describe the necessary apparatus, the method, the relevant equations, and error analysis (if applicable).

In a circuit we need an 8mF capacitor. We only have a 3mF-capacitor, two 6mF-capacitors, and a 4-mF-capacitor at hand. How do we connect the existing capacitors to get the required capacitor?