# ELECTRIC FORCES AND ELECTRIC FIELDS - DOC by q6S4a6Vq

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```									MR. SURRETTE                                                                               VAN NUYS HIGH SCHOOL

CHAPTER 11: ELECTRIC FIELDS AND FORCES
WORKSHEET
(Equations: E = E1 + E2. . ., E = kq/r2, F = kq1q2/r2, k = 9.0 x 109 N.m2/C2, e = 1.6 x10-19 C)

1. At what point is the electrical field associated with a uniformly-charged, hollow, metallic sphere greatest?
(A) center of the sphere (B) at the sphere’s inner surface (C) at infinity (D) at the sphere’s outer surface
(E) within the metal shell

2. Two point charges are placed along a horizontal axis with the following values and positions: +3 C at x = 0 cm and -7
C at x = 20 cm ( = “micro” = 10-6). What is the magnitude of the electric field at the point midway between the two
charges (at x = 10 cm)? [ANS: 9.0 x 106 N/C]

3. Initially, a net charge of – 5.0 C is placed on a 5.0 cm radius metallic hollow sphere. Next, a +10 C charge is carefully
inserted at the center through a hole in the latter’s surface. What electric field is present at a point 10 cm from the center of
the sphere? [ANS: 4.50 x 106 N/C]

4. Two point charges are separated by 5 cm and have charges of + 3.0 C and – 4.0 C, respectively. What is the electric
field at a point midway between the two charges? [ANS: 1.01 x 108 N/C]

5. A Van De Graaff generator has a spherical dome of radius 42 cm. Operating in dry air, where “atmospheric breakdown”
is Emax = 3.00 x 106 N/C what is the maximum charge that can be held on the dome?
[ANS: 58.8 C]

6. A glass rod rubbed with a silk cloth acquires a charge of + 7.40 x 10 -9 C. How many electrons were transferred from the
glass to the silk? [ANS: 4.63 x 1010 electrons]

7. A positive point charge is brought near a neutral conducting sphere. The sphere is isolated from ground. Sketch the
induced charge on the sphere.

8. A positive point charge is brought near a grounded conductor. Sketch the induced charge on the conductor’s surface.

9. What happens to the charge on the above sphere when the positive charge is removed?

10. Three point charges are on the x-axis as shown below. Compute the net force on the 30 micro (30x) coulomb
charge. [ANS: 15 N]

SCIENCE DEPARTMENT

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