Glossary
Charge
A fundamental property of matter that can be positive or negative, determining how it interacts with electromagnetic fields.
Example:
When you rub a balloon on your hair, the balloon gains a net negative charge due to the transfer of electrons.
Coulomb's Constant (k)
The proportionality constant in Coulomb's Law, representing the strength of the electric force in a vacuum.
Example:
The value of Coulomb's constant is very large, indicating that electric forces can be incredibly strong even for small charges.
Coulomb's Law
A fundamental law stating that the electric force between two point charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.
Example:
Using Coulomb's Law, you can calculate the strong attractive force between a proton and an electron in a hydrogen atom.
Coulombs (C)
The SI unit for measuring electric charge, representing the amount of charge transferred by a constant current of one ampere in one second.
Example:
A lightning bolt can transfer many coulombs of charge from the clouds to the ground in a very short time.
Dipoles
A separation of positive and negative charges within an object, creating distinct partial positive and negative ends, even if the object is overall neutral.
Example:
A water molecule is a permanent dipole because its oxygen atom pulls electrons more strongly than its hydrogen atoms, creating partial charges.
Electric Force
The attractive or repulsive force that exists between any two charged objects, acting along the line connecting their centers.
Example:
The electric force is what causes your hair to stand on end when you touch a Van de Graaff generator.
Electrons
Subatomic particles with a fundamental negative charge, whose movement is responsible for electric current and the charging of objects.
Example:
Static electricity often occurs when electrons are transferred between two surfaces, like shuffling your feet on a carpet.
Elementary Charge (e)
The magnitude of the charge of a single proton or electron, which is the smallest discrete unit of charge found in nature.
Example:
The elementary charge is a fundamental constant, meaning all observable charges are integer multiples of this value.
Free-Body Diagram
A visual representation used to analyze forces acting on an object, showing the object isolated from its surroundings with all external forces drawn as vectors originating from the object.
Example:
Before solving a problem involving a block on an incline, drawing a free-body diagram helps visualize gravitational, normal, and friction forces.
Negative Charge
The state of an object or particle that has gained extra electrons, resulting in a net excess of electrons.
Example:
A plastic comb run through dry hair can acquire a negative charge, allowing it to attract small pieces of paper.
Point Charge
An idealized charged particle where the charge is considered to be concentrated at a single, infinitesimally small point in space.
Example:
When calculating the force between two very small, distant charged spheres, they can often be approximated as point charges.
Positive Charge
The state of an object or particle that has lost electrons, resulting in a net excess of protons.
Example:
A glass rod rubbed with silk often develops a positive charge as electrons are transferred from the rod to the silk.
Quantized Charge
The principle that electric charge exists only in discrete, integer multiples of the elementary charge (e), meaning you cannot have a fraction of an electron's charge.
Example:
You can have an object with a charge of +2e or -5e, but never +1.5e, illustrating that quantized charge means it comes in specific packets.
Superposition Principle
The principle stating that the net electric force on a charge due to multiple other charges is the vector sum of the individual electric forces exerted by each of the other charges.
Example:
To find the total force on a central charge surrounded by three other charges, you would use the superposition principle by adding each individual force as a vector.
Vector
A physical quantity that has both magnitude (size) and direction, such as force, velocity, or displacement.
Example:
When describing the wind, stating it's blowing at 20 mph north makes it a vector, unlike just saying 20 mph.