14.8. Electric Circuits Problem Set http://www.ck12.org
a. What is the terminal voltage
b. The external circuit consists of deviceX, 0.5 A and 6 V; deviceY, 0.5 A and 10 V, and two resistors.
Show how this circuit is connected.
c. Determine the value of the two resistors.- Students use a variable power supply an ammeter and three voltmeters to measure the voltage drops across
three unknown resistors. The power supply is slowly cranked up and the following table of data is developed:
TABLE14.5:
Current(ma) VoltageR 1 (v) VoltageR 2 (v) VoltageR 3 (v)
100 2. 1 3. 6 5. 1
150 3. 0 5. 0 7. 7
200 3. 9 7. 1 10. 0
250 5. 0 8. 9 12. 7
300 6. 2 10. 8 15. 0
350 7. 1 12. 7 18. 0
400 7. 9 14. 3 20. 0
450 9. 0 16. 0 22. 0
500 10. 2 18. 0 25. 0
600 12. 5 21. 0 31. 0
700 14. 0 25. 0 36. 0(a) Draw a circuit diagram, showing the ammeter and voltmeter connections.
(b) Graph the above data with voltage on the vertical axis.
(c) Use the slope of the best-fit straight line to determine the values of the three resistors.
(d) Quantitatively discuss the confidence you have in the results
(e) What experimental errors are most likely might have contributed to any inaccuracies.
- Design a parallel plate capacitor with a capacitance of 100 mF. You can select any area, plate separation, and
dielectric substance that you wish. - You have a 5μF capacitor.
a. How much voltage would you have to apply to charge the capacitor with 200 C of charge?
b. Once you have finished, how much potential energy are you storing here?
c. If all this energy could be harnessed to lift you up into the air, how high would you be lifted? - Show, by means of a sketch illustrating the charge distribution, that two identical parallel-plate capacitors
wired in parallel act exactly the same as a single capacitor with twice the area. - A certain capacitor can store 5 C of charge if you apply a voltage of 10 V.
a. How many volts would you have to apply to store 50 C of charge in the same capacitor?
b. Why is it harder to store more charge? - A certain capacitor can store 500 J of energy (by storing charge) if you apply a voltage of 15 V. How many
volts would you have to apply to store 1000 J of energy in the same capacitor? (Important: why isn’t the
answer to this just 30 V?) - Marciel, a bicycling physicist, wishes to harvest some of the energy he puts into turning the pedals of his bike
and store this energy in a capacitor. Then, when he stops at a stop light, the charge from this capacitor can flow
out and run his bicycle headlight. He is able to generate 18 V of electric potential, on average, by pedaling
(and using magnetic induction).
a. If Mars wants to provide 0.5 A of current for 60 seconds at a stop light, how big a 18 V capacitor should
he buy (i.e. how many farads)?