# Homework Help: Charges-Conceptual Question

1. Jul 30, 2013

### Bashyboy

Charges--Conceptual Question

I uploaded a diagram, for I have questions pertaining to it.

First, imagine there no q3 charge. I understand that if there existed no q3 charge, then the two negative charges would assuredly exert repulsive forces on each other. My question is, would this repulsive force cease to exist once the presence of q3 is established between the two positive charges; and would it discontinue to exist even if q3 was unbelievably small? I ask, because once q3 is conceived between the two negative charges, there is no straight line between either negative charge to the other for a component of their electric field to act along, even if q3 were incredible small. Essentially my question is, does the presence of q3 imply that the two negative charges don't exert repulsive forces on each other?

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2. Jul 30, 2013

### voko

The electric field at any location is the (vector) sum of the electric fields due to all the sources. This is known as the superposition principle. What field does $q_2$ experience according to this principle?

3. Jul 30, 2013

### Bashyboy

From what you are saying, the field that q_2 is experiencing is a combination of the field generated by q_1 and q_3. I am having a hard time imagining how q_1's field can manage it's way over to q_2, with q_3 in the way.

4. Jul 30, 2013

### pgardn

Does the presence of the sun change the gravitational force the moon exerts on the Earth?

Does the presence of the sun change the gravitational force the Earth exerts on the moon?

Make the sun Q3 and don't even worry about the alignment.

Oops helped while typing. I was attempting to help answer your essential question.

5. Jul 30, 2013

### voko

That is a property of electric (and magnetic) fields: they propagate through one another unimpeded, and the their net effect is their simple vector sum.

6. Jul 30, 2013

### Bashyboy

Where did you learn this, Voko?

7. Jul 30, 2013

### voko

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