Practice Questions and Correct answers for Electrostatics,
Electric Fields, and Potential
A positively charged rod is brought close to one end of an uncharged metal rod but does not
actually touch it. What type of charge does the end of the metal rod closest to the positively
charged rod acquire? - correct answer The end of the metal rod closest to the positively
charged rod acquires a negative charge.
A plastic rod is rubbed with a fur. During the rubbing process, the rod acquires a negative
charge. What type of charge does the fur acquire? - correct answer The fur acquires a positive
charge.
A rubber rod is rubbed with fur. The fur is then quickly brought near the bulb of an uncharged
electroscope. The sign of the charge on the leaves of the electroscope is - correct answer
positive
A glass marble is rubbed against a piece of silk. As a result the piece of fabric acquires extra
electrons. What happens to the glass marble? - correct answer The marble has lost the same
number of electrons acquired by the piece of silk.
The marble acquires a positive charge and attracts the piece of silk.
Two glass marbles (1 and 2), each supported by a nylon thread, are rubbed against a piece of
silk and then are placed near a third glass marble (3), also supported by a similar thread.
Assuming that marble 3 has not been in contact with the piece of fabric, which of the following
statements best describes the situation when the three marbles are brought together? Ignore
the effects of polarization. - correct answer Marbles 1 and 2 repel each other, but no
interaction occurs with marble 3.
Two charged objects are separated by some distance. The charge on the first object is greater
than the charge on the second object. How does the force between the two objects compare? -
correct answer The charged objects exert electrostatic forces on each other that are equal in
magnitude and opposite in direction.
Two charged objects separated by some distance attract each other. If the charges on both
objects are doubled with no change in distance between them, what happens to the magnitude
of the force between the objects? - correct answer The force between them quadruples.
If the distance between two charged particles is doubled, the magnitude of the electric force
each exerts on the other is changed. If you wanted to change the amount of charge on each of