# Electric Force and Field

1. Sep 27, 2004

### Ezhil

Hi
I was just doing my homework and i am stuck on this question. Can you please help me with this?

a) Caluculate the electric field strength E, at a point located 3.0 cm due east from a point charge q=+1.0 microcoulomb.

I know i have to use the formulas:
E = F/q

And Coulomb's law. But to use Coulomb's law you need to two charges and this question only has one. Please help on this, Thankyou.

Ezhil

2. Sep 27, 2004

### Tide

If the force on q due to Q is
$$\vec F = qQ \frac {\vec r}{r^3}$$
then the electric field due to Q is
$$\vec E = Q \frac {\vec r}{r^3}$$

3. Sep 27, 2004

### Ezhil

Am i right in saying:
E = (k*Qsource) / (r^2)

therefore
E=[(9*10^9)*(1.0*10^-6)] / (0.03)^2
E= 1.0*10^7

4. Sep 27, 2004

### Ezhil

$$\vec E = Q \frac {\vec r}{r^3}$$

What is the vector r equal to and is the Q the point charge 1.0 microcoulomb that is given in the problem?
I'm sorry i don't understand the equation completly, im still in year 11.

5. Sep 27, 2004

### Tide

$\vec r$ is the displacement vector from charge Q to charge q.

6. Oct 6, 2004