Grade 9 Physics
CHAPTER 11.1
Static Electricity
Static Electricity is an imbalance of electric charge on the surface of an object.
● The electric charge that builds up on the surface of an object is called a static charge.
● The charges are “static” because they remain in one location on the surface of an object
until they are given a path to escape.
Atomic Structure
● All matter is made of atoms.
● Atoms contain smaller particles: protons, neutrons, and electrons.
● Some of these particles have an electric charge.
Electric Charge/Positive, Negative, and Neutral Objects
● If an object has more electrons than protons, it is negatively charged (also
called a negatively charged object.
number of protons < number of electrons
therefore, overall charge is negative
● If an object has less electrons than protons, it is positively charged (also
called a positively charged object)
number of protons > number of electrons
therefore, overall charge is positive
, ● If an object has an equal number of protons and electrons, the object is
neutral (also called a neutral object)
number of protons = number of electrons
therefore, overall charge is neutral
● Chemistry Information
○ If an atom loses an electron, it will have one more proton (1+) than electrons,
therefore it has a positive net charge (cation)
○ If an atom gains an electron, it will have one more electron (1e-) than protons,
therefore it has a negative net charge (anion)
Electric Charge Continued
Electric charge is a property of electric charge on the surface of an object. Protons
have a positive charge, electrons have a negative charge, and neutrons have no
charge,
● A charged object and a neutral object will attract each other.
● Electrons can be transferred from one object to another.
○ For example, a neutral or positively charged object will become negatively
charged if it gains electrons.
○ Similarly, a neutral or negatively charged object will become positively charged if
it loses electrons.
● Electrons are capable of moving from one object to another.
● Protons never move.
Law of Electric Charges
,The Law of Electric Charges states that like charges repel while unlike charges
attract.
● LAW OF ATTRACTION: Opposite charges attract
● LAW OF REPULSION: Like charges (positive + positive) repel/stay away from each
other.
● ELECTRIC FORCE: The force exerted by an object with an electric charge; can be a
force of attraction or a force of repulsion.
Electroscope
An electroscope is a device that is used to detect a static charge.
● There are 3 kinds of electroscopes we will see:
○ Pith Ball Electroscope
○ Metal-Leaf Electroscope
○ Needle Electroscope
Spray Painting
https://www.ultrimaxstore.com/blogs/news/the-advantages-of-electrostatic-spray-painting
● Electrostatic paint sprayers use the properties of static charges to more effectively paint
objects. The paint is given the opposite charge as it leaves the nozzle.
● Electrostatic paint sprayers are beneficial because it minimizes the amount of wasted
paint and it is really useful for painting around objects. The process delivers high transfer
efficiency, reduces costs, and can improve environmental performance.
, CHAPTER 11.2
Electron Affinity
● Different substances have different abilities to hold on to electrons
● The tendency of a substance to hold onto the electrons is called electron affinity.
Charging by Friction
Charging by friction occurs when two neutral objects made of different materials
(refer to electrostatic series) rub against or touch each other and electrons are
transferred between them.
● When two objects rub together, the force of friction can remove electrons from one object
and transfer them to the other object.
● As one object loses electrons, the other gains them.
CHAPTER 11.1
Static Electricity
Static Electricity is an imbalance of electric charge on the surface of an object.
● The electric charge that builds up on the surface of an object is called a static charge.
● The charges are “static” because they remain in one location on the surface of an object
until they are given a path to escape.
Atomic Structure
● All matter is made of atoms.
● Atoms contain smaller particles: protons, neutrons, and electrons.
● Some of these particles have an electric charge.
Electric Charge/Positive, Negative, and Neutral Objects
● If an object has more electrons than protons, it is negatively charged (also
called a negatively charged object.
number of protons < number of electrons
therefore, overall charge is negative
● If an object has less electrons than protons, it is positively charged (also
called a positively charged object)
number of protons > number of electrons
therefore, overall charge is positive
, ● If an object has an equal number of protons and electrons, the object is
neutral (also called a neutral object)
number of protons = number of electrons
therefore, overall charge is neutral
● Chemistry Information
○ If an atom loses an electron, it will have one more proton (1+) than electrons,
therefore it has a positive net charge (cation)
○ If an atom gains an electron, it will have one more electron (1e-) than protons,
therefore it has a negative net charge (anion)
Electric Charge Continued
Electric charge is a property of electric charge on the surface of an object. Protons
have a positive charge, electrons have a negative charge, and neutrons have no
charge,
● A charged object and a neutral object will attract each other.
● Electrons can be transferred from one object to another.
○ For example, a neutral or positively charged object will become negatively
charged if it gains electrons.
○ Similarly, a neutral or negatively charged object will become positively charged if
it loses electrons.
● Electrons are capable of moving from one object to another.
● Protons never move.
Law of Electric Charges
,The Law of Electric Charges states that like charges repel while unlike charges
attract.
● LAW OF ATTRACTION: Opposite charges attract
● LAW OF REPULSION: Like charges (positive + positive) repel/stay away from each
other.
● ELECTRIC FORCE: The force exerted by an object with an electric charge; can be a
force of attraction or a force of repulsion.
Electroscope
An electroscope is a device that is used to detect a static charge.
● There are 3 kinds of electroscopes we will see:
○ Pith Ball Electroscope
○ Metal-Leaf Electroscope
○ Needle Electroscope
Spray Painting
https://www.ultrimaxstore.com/blogs/news/the-advantages-of-electrostatic-spray-painting
● Electrostatic paint sprayers use the properties of static charges to more effectively paint
objects. The paint is given the opposite charge as it leaves the nozzle.
● Electrostatic paint sprayers are beneficial because it minimizes the amount of wasted
paint and it is really useful for painting around objects. The process delivers high transfer
efficiency, reduces costs, and can improve environmental performance.
, CHAPTER 11.2
Electron Affinity
● Different substances have different abilities to hold on to electrons
● The tendency of a substance to hold onto the electrons is called electron affinity.
Charging by Friction
Charging by friction occurs when two neutral objects made of different materials
(refer to electrostatic series) rub against or touch each other and electrons are
transferred between them.
● When two objects rub together, the force of friction can remove electrons from one object
and transfer them to the other object.
● As one object loses electrons, the other gains them.
