## Final Exam - Fall 1997

### Answers to Concept and Numerical Questions

1.

1. Is the direction of the uniform magnetic field that is present into or out of the page?  into

2. Which direction is the magnetic force on the electron?  South

3. For what value of the power factor is the impedance purely resistive?  unity
Purely inductive?  zero

4. What is the electric field halfway to the center?  zero
What is the potential halfway to the center?  15 V

6. tend to rotate the loop in a direction such that the magnetic flux increases or decreases?  increases

2.

1. What is the value of the internal resistance? 25 ohm

2. What is the value of the load resistance? 100 ohm

3.

What is the power now delivered to the toaster? 174 W

4.

1. What is the rms current through the toaster? 12.5 A

2. What is the rms current through the capacitor? 4.5 A

3. What is the rms current through the emf? 13.3 A

5.
1. Evaluate the inductance per meter of this flat cable for a pair of wires. 0.67 microH/m

2. Evaluate the capacitance per meter of this flat cable. 16.6 pF/m

3. What fraction of the speed of light is the phase speed? 0.56

4. How long does it take for a signal to travel on a 18 inch flat cable? 2.7 ns

6.
1. Evaluate the capacitance. 14.7 pF

2. How are the charges distributed among the four surfaces?
• #1, inner surface: zero
• #1, outer surface: +1
• #2, inner surface: -1
• #2, outer surface: +2

"http://www.physics.udel.edu/~watson/phys208/exams/fin-97f-ans.html"
Last updated May 19, 1998.
Copyright George Watson, Univ. of Delaware, 1998.