Electric field lines and other topics

[kana]

Please help me answer these?

Please, before you tell me to do my own homework, I've tried doing them. I just need a general idea what to do. No one has to feed me the answers. :'( My professor gave us this homework just today and I only have one day to answer these. I just want to know what to do because I have no idea what to do. I really need a tutor but I can't seem to find anyone who likes Physics. I don't like Physics a lot if it isn't obvious enough. I've tried revising but it's just not helping :'( -- I've already answered 1,2 and 4. They're all I can manage to answer.

 

1. Two small plastic spheres are given positive electrical charges. When they are 15.0 cm apart, the repulsive force between them has magnitude 0.220 N. What is the charge on each sphere (a) if the two charges are equal and (b) if one sphere has four times the charge of the other?

 

2. Two point charges are placed on the x-axis as follows: Charge q1 = +4.00 nC is located at x = 0.200 m and charge q2 = +5.00 nC is at x = -0.300 m. What are the magnitude and direction of the total force exerted by these two charges on a negative point charge q3 = -6.00 nC that is placed at the origin?

 

3. The two charges q1 and q2 shown in Figure 1 have equal magnitudes. What is the direction of the net electric field due to these two charges at points A (midway between the charges), B, and C if (a) both charges are negative, (b) both charges are positive, ©q1 is positive and q2 is negative.

 

4. Three equal 1.20-C point charges are placed at the corners of an equilateral triangle whose sides are 0.500 m long. What is the potential energy of the system? (Take as zero the potential energy of the three charges when they are infinitely far apart.)

 

5. A very long wire carries a uniform linear charge density . Using a voltmeter to measure potential difference, you find that when one probe of the meter is placed 2.50 cm from the wire and the other probe is 1.00 cm farther from the wire, the meter reads 575 V. (a) What is ? (b) If you now place one probe at 3.50 cm from the wire and the other probe 1.00 cm farther away, will the voltmeter read 575 V? If not, will it read more or less than 575 V? Why? © If you place both probes 3.50 cm from the wire but 17.0 cm from each other, what will the voltmeter read?

 

6. A 10.0-F parallel-plate capacitor with circular plates is connected to a 12.0-V battery. (a) What is the charge on each plate? (b) How much charge would be on the plates if their separation were doubled while the capacitor remained connected to the battery? © How much charge would be on the plates if the capacitor were connected to the 12.0 V battery after the radius of each plate was doubled without changing their separation?

 

7. Figure 2 shows a system of four capacitors, where the potential difference across ab is 50.0 V. (a) Find the equivalent capacitance of this system between a and b. (b) How much charge is stored by this combination of capacitors? © How much charge is stored in each of the 10.0-F and the 9.0-F capacitors?

 

8. A plastic tube 25.0 m long and 3.00 cm in diameter is dipped into a silver solution, depositing a layer of silver 0.100 mm thick uniformly over the outer surface of the tube. If this coated tube is then connected across a 12.0-V battery, what will be the current?

[imatfaal]

The more you of your own working you put down the more likely the member will provide hints. For a start perhaps put your answers for 1,2 &4 - and guesses of which equations, laws etc you need to use for others.