### Electric Fields and Potential Homework

1. A test charge of -2 x 10-8 C experiences a force of 0.06 N when placed in an electric field. What is the electric field intensity? Ans: 3 x 106N/C
2. A test charge of +5 x 10-4 C is in an electric field which exerts a force of 2.5 x 10-4N upon it. What is the strength of the electric field? Ans: 0.5 N/C
3. A test charge of +80 mC is placed in a 50 N/C field. What force does it experience? Ans: 0.004 N
4. A +4.9 mC charge produces an electric field of 3.6 x 104 N/C upon a positive test charge. How far away is the charge? Ans: 1.11 m
5. A 19 mC charged sphere produces a 1.7 x 10 3 N/C upon a 0.5 mC test charge. What force is the charge subjected to? How far away is the test charge from the sphere? Ans: 0.00085 N; 10.03 m
6. The electric field intensity between two parallel, charge plates is 8000 N/C. The plates are 0.05 m apart. What potential difference exists between the plates? Ans: 400 V
7. A spark will jump across dry air when the electric field is larger than 1 x 106 N/C. If two parallel plates have a potential difference of 5000 V, how far apart must they be to prevent a spark from jumping across them? Ans: 0.005 m
8. What work is done on a 5 C charge when its electric potential is increased by 1.5 V? Ans: 7.5 J
9. A charge of 50 C is raised in potential by 110 V. What work is done in raising the potential of the charge? Ans: 5500 J

### Capacitors and Oil Drop Homework

1. An oil drop carries a charge of 5 electrons and is balanced in a field of 4.7 x 104 N/C. What is the drop's weight? Ans: 3.76 x 10-14 N
2. A negatively charged oil drop weighs 8.5 x 10-15 N. The drop is suspended in an electric field of 5300 N/C. What is the drop's charge? How many excess electrons does it carry? Ans: 1.6 x 10 -18 C; 10 electrons
3. What is the charge on a 6mF capacitor with a potential difference of 0.60 V? Ans: 3.6 mC
4. A capacitor has a charge of 3 mC and a potential difference of 45 V. What is its capacitance? Ans: 0.067 mF
5. A 0.002 F capacitor has a 6 V potential difference across it. How much energy does it store? Ans: 0.036 J
6. A +26 C charged sphere is touched to a -19 C charged sphere and then removed. What charge remains on each? Ans: +3.5 C