Question

A 3.5 µC charge is uniformly distributed on a
ring of radius 10.5 cm.
Find the electric field on the axis at 1.5 cm
from the center of the ring. The value of the
Coulomb constant is 8.99 × 10
9
N · m2
/C
2
.
Answer in units of N/C

Answer 1

Step 1: draw a diagram.

Now how far is all the charge on the ring from the position 1.5 cm from the center of the ring? That's the distance r you need to use in the Coulomb law calculation

Answer 2

so 10.5-1.5=9
thats the radius i need to use

Answer 3

\[ E = \frac{F}{q_2} = \frac{kq_1q_2}{r^2}\frac{1}{q_2} = \frac{kq_1}{r^2} \]
You know \( q_1 \) and \( k \), and now hopefully you know r.

No ... what you've written there isn't the distance r. Draw a diagram. You will need Pythagorus Theorem.

Answer 4

i just don't get it

Answer 5

The radius of the ring -- the vertical line in this diagram-- is 0.105 m.

The distance from the center of the ring -- the horizontal line in this diagram -- is 0.015 m

Hence the distance of the point of the triangle on the right is by Pythagorus Theorem...

Answer 6

\[ \sqrt{(0.105)^2 + (0.015)^2} \ meters \]

Answer 7

soo..
3.5 *10^-6(8.99*10^9)/(.106067)^2

Answer 8

Looks about right.

Answer 9

thanks!