Glossary
Coulomb's Law
A fundamental law describing the electrostatic force between two point charges, stating it is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
Example:
Using Coulomb's Law, we can calculate the strong repulsive force between two protons in an atomic nucleus.
Dipole Fields
Fields created by two distinct sources, such as two opposite charges or the poles of a magnet, exhibiting more complex behavior than monopoles.
Example:
The field lines around a bar magnet show a classic dipole field pattern, looping from one pole to the other.
Electric Dipole Field
A field created by two equal and opposite charges separated by a distance, with field lines typically curving from the positive to the negative charge.
Example:
A water molecule is a permanent electric dipole due to its bent shape and uneven charge distribution, allowing it to interact with other charged particles.
Electric Field Due to a Single Point Charge
A region of space around a single charged particle where another charged particle would experience an electric force. Its strength is proportional to charge and inversely proportional to the square of the distance.
Example:
A tiny dust particle with a positive charge would feel a push away from a positively charged point charge.
Field Behavior with Distance
Describes how the strength of a field changes as the distance from its source(s) varies, typically decreasing with increasing distance.
Example:
The field behavior with distance for a point charge follows an inverse square law, meaning doubling the distance reduces the field strength to one-fourth.
Gravitational Field
A region of space around a massive object where another massive object experiences a force. Its strength is proportional to mass and inversely proportional to the square of the distance.
Example:
The Earth's gravitational field keeps the Moon in orbit, constantly pulling it towards our planet.
Magnetic Field
A field created by the motion of electric charges (currents) that exerts a force on other moving charges or magnetic materials.
Example:
The Earth's magnetic field protects us from solar radiation, deflecting charged particles away from the planet.
Monopole Fields
Fields that originate from a single source and decrease in strength with distance from that source.
Example:
The light from a single lightbulb spreads out, becoming dimmer the farther you move away, similar to a monopole field.
Point Charge Model
An approximation where a charged object is treated as if all its charge is concentrated at a single point, valid when the object's size is small compared to relevant distances.
Example:
When calculating the electric field far away from a charged sphere, we can often use the point charge model to simplify the calculation.
Test Charge
A hypothetical, infinitesimally small, positive charge used to define the direction and magnitude of an electric field at a given point without disturbing the original field.
Example:
To map out an electric field, physicists imagine placing a tiny test charge at various points and observing the force it experiences.
Vector Addition (of Fields)
The principle that the net field at any point due to multiple sources is found by summing the individual field vectors from each source, considering both magnitude and direction.
Example:
To find the total electric field at a point near two charges, you must use vector addition to combine the fields from each charge.