Practice Problems - Test 1

1.A 2.0 micro Farad capacitor is charged to an electric potential of 12V.  What is the charge stored in the capacitor? (a) 6.0 microC (b) 24 microC (c) 0.17 microC (d) 48 microC

2.What is the energy stored in the electric field in question 1?
(a) 72 microJ  (b) 144 microJ  (c) 288 microJ  (d)  576 microJ

3.Two parallel plates have an electric potential of 50V and are separated by a distance of 10cm.  What is the electric field between the plates? (a) 500 N/C  (b) 5 N/C (c) 5000 N/C (d) 50 N/C

4.Three point charges are located at the following positions: q₁ = 2.0 micro Coulomb at X = 1.0m q₂ = 3.0 micro Coulomb at X = 0.0m q₁ = 2.0 micro Coulomb at X = -1.0mWhat is the force on the 3.0 micro Coulomb charge?

5. Two 3.0mg, 3.0 micro Coulomb charges are located on the ends of a meterstick.  Find the following for the center of the meterstick: (a) The electric field (b) The electric potential

6.How much does it cost to operate a 100 W light bulb (rated at 120V) for a week if electricity costs $0.10 per kWh?
(a) $1680  (b) $16.80  (c) $1.68  (d) $0.17

7.The length of a wire is doubled and the radius is doubled.  By what factor does the resistance change?(a)4 times larger   (b) Twice as large   (c) Unchanged   (d) Half as large

8. A resistor has a current of 2.0 A and a voltage of 50V.  What is the resistance?
(a) 0.040 Ohms (b) 25 Ohms  (c) 100 Ohms (d) 400 Ohms

9. A 12 V battery is connected to a 100 Ohm resistor.
(a) What is the current in the resistor? (b) How many electrons flow through the wire in 10 minutes?

10. A 2500 W heater is connected to a 120V outlet for 10 h.
(a) How much heat is produced in this time?   (b) What is the current? (c) What is the resistance of the heater?

11. Two point charges are separated by a distance d and feel a force F.  What would be the force if the two charges are moved a distance d/3 apart? (9F)

12. How many electrons are required to produce a charge of -6.4 microC? (4x10¹³⁾

13. Electric field lines(a) circle clockwise around positive point charges.(b) circle counterclockwise around positive charges.(c) radiate outward from negative point charges.(d) radiate inward negative point charges.

14.Three charges are located along a straight line, as shown below.  What is the net electric force on charge 
q₂ (F = 0.8 to the left) q₁ = 7.5 microC q₂= -4 microC q₃= 9 microC         |-----------------------|------------------------------|              

 X = 0                       X = 0.4m                            X = 1.0m

15.How much charge can be placed on the plates of a 1x10³ microF capacitor by a 12V battery?  How large a voltage would be required to place the same amount of charge on 1.0 microF capacitor?

16. How much energy is stored by a 25 microF capacitor charged to potential difference of 12V? (1.8 mJ)

17. Which of the following is NOT true.  If placed in an electric field and released, a _____ charge will move to a region of _____(a) positive, lower potential (b) positive, lower potential energy (c) negative, higher potential(d) negative, higher potential energy

18. A capacitor is charged by a charge of 3.0 microC.  What is the capacitance of the capacitor if it is connected with a 5V battery?

19. A 24 Ohms resistor is connected to a 12V battery.  How much current flows through the resistor and how much power is used by the resistor?

20. A wire carries a current of 5.0A.  How many electrons cross a given area of the wire each second? (3.1x10¹⁹)

21. Two parallel plate capacitors are identical except that one is air-filled an other is filled with a dielectric material
k = 10.5.  How much larger is the capacitance of the dielectricfilled capacitor than the air-filled capacitor? (10.5)

22. At what temperature would the resistance of a silver conductor be double its resistance at 20.0 deg?  Take the temperature coefficient of resistivity for silver to be 3.8x10^-3 /deg C. 

23.The resistance of a copper wire is 25 Ohms.  If the wire's cross-sectional area is 3.4x10^-6  sq meters, what is length of the wire?

24.What is the equivalent capacitance of a parallel combination of 12, 6, and 25 microF capacitors?  Similarly what happens if they are connected in series?

 
bhatti@panam.edu