Below you will find a set of 5 conceptual and numerical revision questions selected randomly from lots of questions I have put together covering the material in Chapter 21, "The Electric Field I: Discrete Charge Distributions". This includes questions on charges, conductors and insulators, Coulomb's Law, electric field and electric dipoles. When you have finished the quiz, click on the "Submit Quiz" button at the bottom and within seconds it will be automatically graded and the results returned to you!

To select a new set of questions click on the "Reload" or "Refresh" button on your browser. You may find some of the questions duplicated but that's the nature of a random selection. Try it a few times ... it's not fattening and you may learn something!

Many thanks to Mark Wood for producing the quiz-maker code.

Q1: Two identical conducting spheres carry charges of +5.0 μC and -1.0 μC, respectively. The centers of the spheres are initially separated by a distance L. The two spheres are brought together so that they are in contact. The spheres are then returned to their original separation L. What is the ratio of the magnitude of the force on either charge after the spheres are touched to that before they were touched?

1/1
4/5
9/5
5/1
4/9

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Q2: Two point charges, A and B, lie along a line separated by a distance L. The point x is the midpoint of their separation.

Which combination of charges will yield zero electric field at the point x ?

+1q and -1q
+2q and -3q
+1q and -4q
-1q and +4q
+4q and +4q

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Q3: The force between two very small charged bodies is found to be F. If the distance between them is doubled without altering their charges, the force between them becomes

F/2
2F
F/4
4F
1/F²

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Q4: Three positive and equal charges Q₁, Q₂, and Q₃ are at the corners of an equilateral triangle as shown below.

Point P is at the midpoint of the line between Q1 and Q3. The electric field at P is

zero
not zero and is directed along the line from P to Q₃.
not zero and is directed along the line from P to Q₂.
not zero and is directed along the line from Q₁ to Q₂.
None of these is correct.

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Q5: Five particles are shot from the left into a region that contains a uniform electric field. The numbered lines show the paths taken by the five particles. A negatively charged particle with a charge -3Q follows path 2 while it moves through this field.

Which path would be followed by a helium atom?

1
2
3
4
5

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