PHYS345 First Midterm Exam October 8, 1998
Does the emf lead or lag the current?
Does the voltage across the current source increase or decrease?
Construct the Thevenin generator that would represent this circuit.
- VTH = 12 V;
RTH = 6 ohm
- What is the current through the lamp?
- 0.20 A
- What is the terminal voltage of the AAA cell?
- 1.38 V
- What is the current through the lamp now?
- 0.23 A
- What is the terminal voltage of the AAA cell now?
- 1.61 V
- Was adding the 9 V battery worth it?
- No, of the 3.7 W delivered by the additional battery,
3.0 W is wasted by its internal resistance.
- Operated at 120 V, what is the current through the motor when operated at 60 Hz?
- 17.9 A \/ -63.4 deg
- What power is delivered by the voltage source?
- 960 W
- What power is dissipated by the motor?
- 960 W
- What is the power factor of this circuit at 50 Hz?
- What capacitance do you need to correct the power factor back to unity?
- 470 uF
- What power should the resistor be able to dissipate adequately
to conduct this test successfully?
- around 14W
- A current of 1.10 A is measured with the DMM.
What is the internal resistance of the battery?
- 0.91 ohm
What is the resistance of the starter motor?
- 0.10 ohm
Last updated Oct. 15, 1998.
Copyright George Watson, Univ. of Delaware, 1998.