NAME____________________________
SNC1D3
STATIC ELECTRICITY PROBLEMS
1) The diagram to the right shows a thundercloud.
a)
Why does the tree below the thundercloud become positively charged?
Cloud induces a + charge, since – cloud repels –s in tree, they repel into
ground, leaving + charges in tree
b)
What type of charging is occurring? induction
c)
How do engineers reduce the risk of damage to tall buildings due to
lightning strikes? Use lightning rods, metal poles to take the charge away
from damaging buildings
d)
Why are lightning rods made of copper? It’s a conductor that will transfer
charges into the ground.
2) Bicycle frames can be painted using electrostatic paint spray. Typically the
frame of the bicycle is given a net negative charge.
a)
Using the diagram above, EXPLAIN why the paint droplets are all given a positive charge. + will attract to – frame, so paint
will only attract to frame
b)
What would happen in the paint droplets were given a negative charge instead of a positive charge? They would repel the
frame and not land on the frame.
3) The diagrams below show the stages of an experiment to charge spheres. EXPLAIN what type of charging occurred and briefly
state what is happening at each stage. Charging by induction
Neutral A & B spheres
- rod repels – charges to B
spheres are separated with – rod
A is +, B is -
4) When a polythene strip is rubbed with a woollen cloth, the strip becomes negatively charged.
a) Complete the THREE spaces below in the diagram.
Polyethylene is – because it has more electrons
Woolen cloth now has positive charge because it has
fewer electrons
Polythene strip
now has a
negative charge
because it has more
...................................
b) Why does the charge remain on the
polythene strip? It is an insulator which has
a strong affinity for electrons
Woollen cloth
now has a
................................... charge
because it has fewer
...................................
c) Why would a copper strip NOT become
charged if it was rubbed with a woollen
cloth? It is a conductor which does not
hold charges well
5) A student did an experiment using the following instructions.

Take a polythene rod (AB), hold it at its centre and rub both ends with a cloth.

Suspend the rod, without touching the ends, from a stand using a stirrup and nylon thread.

Take a rubber rod (CD) and rub it with another cloth.

Without touching the ends of the rubber rod, bring each end of the
rubber rod up to, but without touching, each end of the polythene rod.

Make notes on what is observed.
C
The diagram to the right shows how the apparatus is to be set up.
Wooden
stand
a)
Why did the student need to use a wooden stand in the experiment? Wood is an
insulator so it would not conduct the charges through the rod and thread
b)
When end C was brought near to end B, they attracted each other.
EXPLAIN why they attracted each other. The polyethylene and rubber must
be charged oppositely since they attract. So whatever cloths were used to
them, 1 cloth made 1 object +, and the other cloth made the other object -.
A
B
D
charge
c)
What would happen if end C were brought near end A? JUSTIFY your reasoning. Should still attract since the entire rod
was charged with the same cloth, A and B should have the same charge, C and D should have the same charge.
d)
The experiment was repeated except with two polythene rods.
DESCRIBE
what you would expect the student to observe as the end of one rod was brought near the end of the other. JUSTIFY your
reasoning. If 2 of the same rods are charged with the same cloth, they should have the same charge, meaning they would
repel, since like charges repel.
e)
EXPLAIN, in terms of electron movement, what happened as the rods were rubbed with the woollen cloths. Assuming the
cloth has weaker affinity for electrons, the rods have a stronger affinity for electrons would take charges from the cloth,
making them – and the cloth +.
6) A light, small Styrofoam ball (pithball) is painted with a metallic paint and attached to a string that hangs freely in mid–air.
a)
What will the pithball do when a positively charged rod is brought close to it (the two DO NOT touch)? It will attract since
neutral attracts charged objects
b)
How would the results of part a) have changed if the rod had been negatively charged? Results would be the same since
opposites attract and neutral attracts charged objects.
c)
The rod and the pithball in part a) touch. What will happen next? The pithball would also become + charged since –s from
the pithball will go onto the rod.
Below are five diagrams of a metal sphere which is insulated from the ground. The + and – signs indicate the sign of the NET charge
on the left and right sides of the sphere or the overall charge. For each of the procedures described below, place the letter of the
diagram that BEST represents the resulting NET charge on each side of the sphere.
7) ___B__
A positively charged rod is brought near, but not touching the left side of a neutral sphere.
8) __D___
A plastic rod is charged positively by rubbing it with felt. The felt is then touched to a neutral sphere and
later removed.
9) __D___
A positively charged rod is brought near a neutral sphere, the sphere is charged by induction and the rod
is then taken away.
10) __C___
A sphere is charged by contact with a positive rod.
11) __B___
A negatively charged rod is brought near but not touching the right side of a neutral sphere.
12) __C___
A positively charged rod is brought near the right side of a sphere that was already positively charged.
13) __C___
A person holding a metal rod touches it to a positively charged sphere.