- #1
JosephK
- 40
- 2
Homework Statement
A uniformly charged insulating rod of length 14.0 cm is bent into the shape of a semicircle. The rod has a total charge of -7.50[itex]\mu[/itex]C. Find (a) the magnitude and (b) the direction of the electric field at O, the center of the semicircle.
Homework Equations
d[itex]\overline{E}[/itex] = [itex]\frac{k dq}{r^2}[/itex][itex]\widehat{r}[/itex]
The Attempt at a Solution
This is a continuous charge distribution. The electric field points in the +x direction.
I made dq = [itex]\lambda[/itex]d
and integrated
[itex]\overline{E}[/itex] = [itex]\int[/itex][itex]\frac{k dq}{r^2}[/itex][itex]\widehat{r}[/itex]
from 0 to l, where l is the length of the rod
This is incorrect because r is constant.
R can be found through geometry.
I did not understand how to use cos[itex]\theta[/itex].
I reasoned at the ends of the rod, the angle is 90.
I did not figure out what angle it is.