# Homework Help: Charge on the dust particle?

1. Jan 19, 2010

### Kourtney0115

1. The problem statement, all variables and given/known data

A small piece of dust of mass m = 1.6 g travels horizontally through an electric air cleaner in which the electric field is 508 N/C. The electric force on the particle is equal to the weight of the particle.
a)What is the charge on the dust particle?
b)If this charge is provided by an excess of electrons, how many electrons does that correspond to?

2. Relevant equations
E=F/q

3. The attempt at a solution
a. (1.6e-6 * 9.8)/508 = 3.1e-8
b. 3.1e-8/1.6e-19 = 1.94e11

2. Jan 19, 2010

### kuruman

Hi Kourtney0115, welcome to PF. Is there an answer you are seeking? If so, what is the question?

3. Jan 19, 2010

### Kourtney0115

I attempted questions a and b from my question i posted but when i put it into my online homework it says its incorrect. I wasnt sure what i was doing wrong.

4. Jan 19, 2010

### kuruman

1.6 g = 1.6x10-3 kg. You are off by three orders of magnitude. Otherwise, your method is correct.

5. Jan 19, 2010

### Kourtney0115

The reason i used 1.6x10^-6 is because it is supposed to say 1.6 micrograms. the symbol didnt paste with the rest of the problem. sorry about that.

6. Jan 19, 2010

### Stonebridge

If it's micrograms then it should be 1.6x10-9 kg. (=1.6x10-6 g)

7. Jan 19, 2010

### Kourtney0115

Ok, thank you so much!!

8. Jan 19, 2010

### kuruman

Then 1.6 micrograms = 1.6x10-6 grams = 1.6x10-9 kg.

9. Jan 19, 2010

### Jayjubear

Oh hi Purdue Physics 221. I just got done with this one.