Name: _EXAMPLAR_ Partner: _____________________ Date: _____________________
SNC 1D- Charging by Friction and Contact, and Induced charge seperation lab
Introduction
Matter has the ability to obtain a charge. Matter that has an equal number of electrons and
protons is considered to be neutral. Matter that has more electrons than protons will be positively
charged and matter that has more electrons than protons will be negatively charged. According to the
law of electric charges, opposite charges attract each other whereas like charges repel each other.
Using observation based on attraction or repelling, the charges of matter can be determined. The
purpose of this lab will be to observe and explain the effects of charging by friction and contact as well
as charge separation by induction.
Materials:
Metal leaf electroscope
ebonite rod
animal fur
PART A – Charging by CONTACT
Procedure:
1. Touch the metal knob of the electroscope with your hand to ground any surplus charge that the
electroscope may have. Do the same with the ebonite rod. They are now both neutral.
2. Touch the ebonite rod to the metal knob of the electroscope and record what you observed in
Table 1.
3. Rub the ebonite rod with the fur and then touch it to the metal knob of the electroscope. Record
what you observed in Table 1.
Table 1. Qualitative observations of charging by contact.
Experiment
Observations (Be specific!)
Contact with a neutral rod
When the rod touched the metal knob, the
leaves did not attract nor repel.
Contact with a charged rod
When the rod touched the metal knob, the
leaves repelled each other. They continue to
repel each other when the rod was removed.
PART B – Charging through INDUCTION
Procedure:
1. Touch the metal knob of the electroscope with your hand to ground any surplus charge that the
electroscope may have. Do the same with the ebonite rod. They are now both neutral.
2. Place the ebonite rod near the metal knob of the electroscope (DO NOT TOUCH THE KNOB)
and record what you observed in Table 2.
3. Rub the ebonite rod with the fur and then place the ebonite rod very close to the metal knob of the
electroscope (DO NOT TOUCH THE KNOB). Record what you observed in Table 2.
Table 2. Qualitative observations of induction.
Experiment
Induction with a neutral rod
Induction with a charged rod
Observations (Be specific!)
When the rod was brought close to the metal
knob, the leaves did not attract nor repel.
When the rod was brought close to the metal
knob, the leaves repelled each other. When the
rod was removed the leaves no longer repelled
each other and came back to a vertical position.
Discussion
Answer these questions in several paragraphs. Be as specific as possible in your explanations!!
1. What type of charging occurred when the rod was rubbed with the fur? What charge was obtained
on the rod and why?
The type of charging that occurred between the rod and the fur was charging by friction. The rod
obtained a negative change and the fur became positive. The rod (ebonite) has a stronger hold on
electrons than fur and therefore took some electrons from the fur which has a weaker hold on the
electrons.
2. Explain in detail both results for PART A and then both for PART B (i.e. why did each happen).
Use a diagram to help explain each observation. Make them large and clear. Include both positive and
negative charges. Show the movement of charges if any.
PART A - Contact with a neutral rod
When the neutral touches the knob no electrons are transferred keeping the knob neutral. Since the
leaves are connected to the knob, the leaves remain neutral and do not attract nor repel.
Diagram
PART A - Contact with a charged rod
When the negatively charged rod touches the knob, electrons are transferred to the knob. This is
charging by contact. Now both the rod and knob are negative. The electrons inside the knob spread out
as they repel each other. When spreading out the electrons move down to the leaves making the leaves
negatively charged. Since the leaves are both negatively charged they repel each other.
Diagram
PART B - Induction with a neutral rod
When the neutral comes close to the knob, there is no repulsion or attraction on the knob’s electrons.
The knob and leaves remain neutral and do not attract nor repel.
Diagram
PART B - Induction with a charged rod
When the negatively charged rod comes close to the knob but does not touch it, the rod’s negative field
repels the electrons that are in the knob. No electrons are transferred from the rod to the knob. The
electrons in the knob move as far away from the rod as possible. This causes them to move down to the
leaves. When the electrons move down to the leaves it makes the leaves negatively charged. Since the
leaves are both negatively charged they repel each other. When the rod is pulled away, there is no
longer a repelling force from the rod above. The electrons in the leaves now spread out again and some
enter back into the knob. The leaves are now back to neutral and they no longer repel each other.
Diagram