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clairez93

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## Homework Statement

1. A thin rod bent in the shape of a semicircle of radius 20 cm is uniformly charged along its length with a total charge of 8.0 microC. What is the electric field at the center of the semicircle?

a. 7.3 x 10^4 N/C

b. 8.4 x 10^4

c. 5.7 x 10^4

d. 3.9 x 10^4

e. None

Answer: C

2. Two charges, q1 = +2.0 microC and q2 = -3.0 microC are placed on the two corners A and B of a square as shown. What should be the value a charge q3 placed at the corner D such that the net electrostatic force on a test charge Q on corner C is zero?

a. 3.0 microC

b. -3.0

c. -2.0

d. +2.0

e. None

Answer: E

3. Two charges of +5.0 microC are placed on two corners of an equilateral triangle of side 0.50 m. The magnitude of the electric field at the third corner is:

a. 3.9 x 10^3 N/C

b. 2.8 x 10^4

c. 1.6 x 10^5

d. Zero

e. None

Answer: C

4. A charge of +3.0 microC is located at the origin and another charge of -4.0 microC is located on the y-axis at y = 0.30 m. The magnitude of the electric field at 0.40 m is:

a. 2.5 x 10^3 N/C

b. 3.2 x 10^4

c. 5.7 x 10^4

d. 9.5 x 10^4

e. None

Answer: D

5. The figure shows two 5.0 g spheres suspended from 1.0-m-long threads. The spheres repel each other after being charged to +31 nC. What is the angle theta?

a. 4.0 degrees

b. 6.0

c. 2.0

d. 7.9

Answer: C

6. Three charges of magnitude 9.0 x 10^-4 C each are located at x = 1.0m, y = 0.0 m, at x = 0.0 m, y = 0.0 m, and a t x = -1.0 m, y = 0.0 m. The one in the middle is negative, while the other two are positive. What is the net Coulombic force exerted by them on a negative 9.0 x 10^-5 C charge located at x = 0.0 m, y = -2.0 m?

a. 790 N repulsive

b. 1100 N attractive

c. 1100 N repulsive

d. 790 N attractive

Answer: D

## Homework Equations

## The Attempt at a Solution

*see pictures*

For second 3:

http://img695.imageshack.us/img695/8262/electrostatics4.jpg

http://img189.imageshack.us/img189/3112/electrostatics5.jpg

http://img706.imageshack.us/img706/4039/electrostatics6.jpg

#### Attachments

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