Electricity and Magnetism: The Art of Conserving Electricity
Lesson 1: Electric Charge and Static Electricity
Lesson 2: Coulomb's Law
Lesson 3: Electric Field
Lesson 4: Electric Potential
All matter is composed of atoms containing electrons, protons, and neutrons.
Neutral Objects: Contain equal numbers of electrons and protons.
Charged Objects: Imbalance in the number of electrons and protons results in an electrical charge. Neutrons do not participate in electric interactions.
An object with more electrons than protons is negatively charged.
An object with more protons than electrons is positively charged.
The electric imbalance can be extremely small, e.g., 1 imbalance per 10 trillion particles.
Electric charge is conserved: charge cannot be created or destroyed, only transferred.
Charged objects exert electric forces on each other: Opposite charges attract, like charges repel.
Electrostatic Series: Rubbing materials together can result in charge transfer, determined by their position in the series.
Example: Rubbing rubber with fur can produce a negative charge on rubber.
Occurs when a neutral object contacts a charged object.
Excess electrons from the charged object may transfer to the neutral one (if negative).
If both objects are conductive spheres, they will share equal charge after contact.
Charge resides on the surface due to electron repulsion.
A charged object is brought near (not touching) a neutral object, which is connected to a distant object (e.g., Earth).
This produces a redistribution of charge, resulting in the neutral object acquiring an opposite charge.
Defined as an imbalance of electric charge within or on the surface of a material.
Describes the force between two point charges (F):
Formula: F = k (q1 * q2) / r²
Where k is Coulomb's Constant (9.0 x 10⁹ Nm²/C²)
Charge relationships:
Force is stronger as distance decreases.
For two 3C charges, at a distance of 50 cm, the force can be calculated using the formula:
F = k (q1 * q2) / r², yielding F = 0.324 N.
A physical field surrounding charged particles exerting forces on other charges.
Visualized as lines indicating direction (attracting or repelling).
Defined as the force per charge experienced by a test charge.
Units: Newtons per Coulomb (N/C).
Electric Field Strength formula: E = F / q
Coulomb’s Law: F = k (q1 * q2) / r²
Visual representation of electric fields, showing direction and strength.
Lines do not cross; proximity of lines indicates strength.
By convention, lines point away from positive charges and toward negative ones.
Electric potential energy is crucial for daily life, derived from energy produced in generating plants.
Voltage: Measure of electric potential energy needed to move a charge against an electric field.
Energy required to move a charge against an electric field varies with distance and field strength.
Example: Energy differences illustrated with light bulbs and electrical devices in their inactive states.
Defined as the difference in electric potential between two points in an electric field.
Voltage influences how much work is done on a charge to alter its potential energy.
Electric Potential (V): The electric potential energy per unit charge.
Formula: V = U / q, where U is electric potential energy and q is the charge.