Download Electric Fields

SPH 4U
Electric Fields Worksheet
http://library.thinkquest.org/10796/ch12/ch12.htm
Concept
1.
Suggest a simple reason why two electric field lines can never cross. (Hint: Consider the field at
the point where they would cross, and imagine that you are a small test charge.)
2. Why do we use a "small" test charge to detect and measure an electric field?
3. If a charged particle is free to move in an electric field, in what direction will it always travel?
4. Three small, negatively charged spheres are located at the vertices of an equilateral triangle.
If the magnitudes of the charges are equal, sketch the electric field in the region around this
charge distribution, including the space inside the triangle.
Problems
5. Two small, oppositely charged spheres have a force of electric attraction between them of 1.6 x
10-2 N. What does this force become if each sphere is touched with its identical, neutral mate,
and then replaced twice as far apart as before? The mates are taken far away. (1.0 x 10-3 N)
6. A small test charge of + 1.0 C experiences an electric force of 6.0 x 10-6 N to the right.
(a) What is the electric field intensity at that point? (6.0 N/C [right])
(b) What force would be exerted on a charge of -7.2 x 10-4 C located at the same point, in place
of the test charge? (4.3 x 10-3 N [left])
7. What is the magnitude and direction of the electric field 1.5 m to the right of a positive point
charge of magnitude 8.0 X 10-3 C? (3.2 x 107 N/C)
8. What is the magnitude and direction of the electric field at point Z in the diagram below?
(5.8 x 105 N/C [right])
9. The electric field intensity at a point between two large parallel plates is 4.8 x 10 2 N/C. What
does the electric field become, as a result of each of the following changes, considered separately (the plates are isolated):
(a) when the distance between the plates is halved? (4.8 x 102 N/C)
(b) when the amount of charge on each plate is tripled? (1.4 x 103 N/C)
(c) when the plates are connected together by a conducting wire? (0)
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