Glossary
Charge Distribution on Conductors
The way excess electric charge arranges itself on the surface of a conductor in electrostatic equilibrium, spreading out to maximize the distance between charges.
Example:
On an irregularly shaped conductor, the charge distribution on conductors will be densest at points with the smallest radius of curvature, like sharp corners.
Conductor
A material that allows electric charge to move freely through it due to the presence of mobile charge carriers, typically free electrons.
Example:
Metals like copper are excellent conductors, which is why they are widely used for electrical wiring in homes and devices.
Current Flow
The directed movement of electric charges, typically electrons, through a conductor when a potential difference (voltage) is applied across it.
Example:
Connecting a battery to a circuit causes current flow, illuminating a light bulb.
Electric Field (in conductors)
The force per unit charge experienced by a test charge; it is always perpendicular to the surface of a conductor and zero inside the conductor in electrostatic equilibrium.
Example:
Outside a charged conducting plate, the electric field lines are perpendicular to its surface, but inside the plate, the field is nonexistent.
Electric Potential (in conductors)
The amount of work needed per unit charge to move a test charge from a reference point to a specific point; it is constant throughout a conductor in electrostatic equilibrium.
Example:
All points on the surface and within a charged conducting sphere are at the same electric potential, even if the charge distribution isn't uniform.
Electrostatic Equilibrium
A state in which there is no net motion of charge within a conductor, meaning all charges are stationary and the electric field inside is zero.
Example:
When a charged metal sphere is isolated, it quickly reaches electrostatic equilibrium as its excess charges redistribute themselves on the surface.
Faraday Cage
An enclosure made of a conducting material that blocks external static and non-static electric fields, creating a region of zero electric field inside.
Example:
A microwave oven acts as a Faraday cage, containing the electromagnetic waves within its interior to cook food safely.
Free Electrons
Electrons in a material that are not tightly bound to individual atoms and can move throughout the material, enabling electrical conduction.
Example:
The abundance of free electrons in a silver wire makes it an excellent conductor of electricity.
Gauss's Law
A fundamental law in electromagnetism that relates the electric flux through any closed surface to the net electric charge enclosed within that surface.
Example:
Using Gauss's Law, one can easily calculate the electric field produced by a uniformly charged infinite plane or a spherical charge distribution.
Induced Charges
Charges that appear on the surface of a conductor due to the presence of an external electric field or nearby charges, without direct physical contact.
Example:
When a negatively charged balloon is brought near a neutral metal can, positive induced charges accumulate on the side of the can closest to the balloon.
Shielding/Screening
The phenomenon where a conductor rearranges its internal charges to cancel out any external electric field within its bulk, protecting the interior.
Example:
Sensitive laboratory equipment is often placed inside metal enclosures to provide shielding from stray electromagnetic interference.
Zero-Field Zone
The region inside a conductor in electrostatic equilibrium where the net electric field is always zero, regardless of external fields or charges on the conductor.
Example:
A person inside a car during a lightning strike is safe because the car's metal frame creates a zero-field zone within its interior.