Grade Nine Science
SNC 1D
Static Electricity Note
Review of Atomic Structure:
The Typical Atom
The nucleus is the small region in the middle of the
atom that contains protons and neutrons.
Neutrons have almost the same mass as protons but
carry no electric charge.
Electrons move around the nucleus and have 1/2000
the mass of a proton.
Usually the atoms of everyday matter have the same
number of electrons as protons. Atoms are
electrically neutral.
When atoms gain electrons they are electrically
negative. The atom has become a negative ion since
it has more electrons than protons.
When atoms lose electrons they are electrically
positive. The atom has become a positive ion since
it has more protons than electrons.
Nelson Physics 11
Protons are fixed in the nucleus and are not lost or
gained by atoms unless a nuclear reaction occurs.
Charge and Macroscopic Objects
The atoms of an electrically neutral object can gain electrons and become a negatively charged object or
lose electrons and become a positively charged object. The build up of stationary charges (electrostatic
charge) on an object is called static electricity. An object which has an excess of electrons has a negative
charge, an object which has a deficiency of electrons has a positive charge. Materials that make up objects
fall into two main categories conductors and insulators.
CONDUCTORS
electrons move easily
don't hold electrostatic charge
many are metals
Chapter 9 Nelson
INSULATORS
electrons don't move easily
hold electrostatic charge
many are nonmetals
Example: A plastic comb pulled through your hair will gain electrons from your hair and gain a negative
charge. The hair has lost electrons and gained a positive charge. Notice protons have nothing to do with the
charging of objects.
Interaction of Charges
The interaction of charged particles/objects can be studied using the Laws of Electric Charge.
Laws of Electric Charge
Like charges repel each other.
Unlike charges attract each other.
Charged objects can attract neutral objects.
Charging Objects
Objects can be given an electric charge in three main ways; charging by friction, charging by contact and
charging by induction.
Charging by friction
Two objects made of different materials are rubbed together, an example is rubbing a glass rod with silk.
One of the materials (silk) has a stronger attraction for electrons than the other material (glass). The
material with the stronger electron attraction (silk) gains electrons and becomes negatively charged, the
other material (glass) loses electrons and becomes positively charged.
The strength of a material's attraction for electrons has been studied and quantified. It is summarized in a
table called the electrostatic series (Table 1).
Chapter 9 Nelson
Chapter 9 Nelson