Electric Fields- 2 Dimensions

1. Jan 24, 2009

AbbyGirl

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

Use Coulomb's law to determine the magnitude and direction of the electric field at points A and B in Fig. 16-57 due to the two positive charges (Q = 4.0 µC) shown.

3. The attempt at a solution

Basically, I'm completely lost. I've applied Coulomb's law to find the magnitudes of the contributing electric fields.

Can anyone help me solve this problem/ at least get started. Thanks so much, god bless.

2. Jan 24, 2009

Copycat91

Apply Coulomb's law for each charge separately.
Then use vector superposition once you find electric field for each charge.

3. Jan 25, 2009

chrisk

An electric field is a vector so it has a magnitude and a direction. Using Coulomb's Law gives an expression for E:

$$\vec{E}=\frac{\vec{F}}{q}\mbox{ where q is a test charge}$$

$$\vec{F}=\frac{qQ\hat{r}}{4\pi \varepsilon_0 \ r^2}$$

$$\mbox{where }\hat{r}\mbox{ is the unit vector in the r direction}$$

So,

$$\vec{E}=\frac{Q\hat{r}}{4\pi \varepsilon_0 \ r^2}$$

where r is the distance from the charge to the point in question. Resolve E into Ex and Ey using cosine and sine. Then add these resolved components to find the resultant components.