# Homework Help: Electricty sort of

1. Jan 25, 2004

### Spectre32

Ok i have a rather simple question at hand:

1 gram of Siliver has 5.58x10^21 atoms and each sliver atom has 47 electrons : How many electrons are in 2 grams of sliver...
This is easy enough, all i did was take 5.58x10^21 and multiply 2 and then divided that number by 47 and got: 2.37447 x10^20

Now the second part to this problem wants to know the total charge of these electrons, and the answer needs to be in units of C. This is the part that i'm schetchy on. IF anyone could provide anyinsight i'm be very greatful.

2. Jan 25, 2004

### Staff: Mentor

Don't divide by 47... multiply!
Look up the charge of the electron.

3. Jan 25, 2004

### Spectre32

God... that was easy enough.... since that one was sloved so quick i got another one for you. This involves 2 glass spheres. These two spheres are touching. Then a 3rd glass sphere is brought near and is charged neg. a groud wire it attached to the 2nd spehere( both spheres are still touching) then the wire is taken away, and then the neg charged sphere is takin away. Then the spheres are seperated. It's a multple choice question with about 10 answers. Now here is what i am thinking. When the neg sharged sphere comes closew the charge is transfered. with the grounding wire comming into ply the charge is now gone. Once the wire is remoived and the neg sphere is still there the other soheres become charged negativitly. Once the neg sphere is removed they are still charged and then where they are seprated.. (this is where things become fuzzy)I wanna say that they both are now negativtly charged. Any help would be awsome.

4. Jan 26, 2004

### Staff: Mentor

Since glass is an insulator, a grounding wire should have little effect. I say the charge of the two glass sphere will not change. If they started out with no charge, they will end up with no charge.

5. Jan 26, 2004

### Spectre32

ok so anything that involves a "glass sphere" isn;t going ot have a charge due to it being a insulator?

6. Jan 26, 2004

### Staff: Mentor

Not correct. An insulator can certainly be charged. What an insulator cannot do is conduct charge--in other words the charge is fixed, not free to move about.

7. Jan 27, 2004

### Spectre32

Ahh i see, and i was wrong in my wording. The spheres are not made out of glass there on glass rods... so they are conducting, and i'm noe even more confused.

8. Jan 27, 2004

### Staff: Mentor

This is very different! This time you'll end up with a positive charge on the two conducting spheres.

Here are the details. When the negatively charged object is put next to one of the conducting spheres, a positive charge is induced on the surface of the conductor nearest the charge. A negative charge appears on the opposite surface (on the 2nd conducting sphere). When that sphere is grounded, the negative charge escapes; but the positive charge is bound because of the field of the charging object. When the wire and the charging object are removed, the net positive charge remains (no place to go!) and distributes itself between the two conducing spheres. When you separate them, you end up with two positively charged spheres. Make sense?

9. Jan 27, 2004

### Spectre32

yeah it makes perfect sense, but does it matter tha the groundering wire is removed and THEN the negatively charged object is removed?

10. Jan 27, 2004

### Staff: Mentor

Absolutely. Do it in the opposite order and you'll end up with no net charge on the conducting spheres.

11. Jan 27, 2004

### Spectre32

Well thats how this problem is set up, the grounding wire is cut, and then the chargin sphere is removed. So then the approite answer is that both spheres are no net charged.

12. Jan 27, 2004

### Staff: Mentor

Nope. "No charge" would be the answer for the opposite case: first remove charging sphere, THEN cut wire.

13. Jan 27, 2004

### Spectre32

AH! I see now! YEs it's all so clear. Thanks, I have a few more questions, you seem knowledgeable do u mind if i ask them?

14. Jan 28, 2004

### Staff: Mentor

Ask away. But put new questions in a new thread with a descriptive title.