Glossary
Capacitance
A measure of a capacitor's ability to store electric charge, defined as the ratio of charge stored to the potential difference across its plates.
Example:
A large camera flash unit requires a high capacitance to store enough charge to release a bright burst of light quickly.
Dielectric constant (k)
A dimensionless value that indicates how much a material can be polarized, representing the factor by which a dielectric increases the capacitance of a capacitor.
Example:
Water has a high dielectric constant of 80, making it effective at reducing the electric field between charges, which is why it's a good solvent for ionic compounds.
Dielectrics
Insulating materials that, when inserted into a capacitor, increase its capacitance by allowing more charge to be stored at the same voltage.
Example:
A smartphone uses a thin layer of dielectric material in its touchscreen to precisely detect finger touches by changing the local capacitance.
Electric field
The force per unit charge experienced by a test charge, which is weakened within a dielectric material due to the induced electric field from polarization.
Example:
Inside a microwave oven, the electric field oscillates rapidly, causing water molecules to rotate and generate heat through friction.
Energy stored
The electrical potential energy stored within a capacitor's electric field, which decreases when a dielectric is inserted if the capacitor is disconnected from a battery.
Example:
The energy stored in a defibrillator's capacitor is rapidly discharged to deliver a life-saving electrical shock to a patient.
Gauss's Law
A fundamental law relating the electric flux through a closed surface to the net charge enclosed, modified by the dielectric constant when a dielectric is present.
Example:
Engineers use Gauss's Law to calculate the electric field distribution around charged conductors, like the shielding effectiveness of a Faraday cage.
Insulating materials
Materials that do not conduct electricity well, often used in capacitors to prevent charge flow and enable polarization.
Example:
The plastic coating around an electrical wire is an insulating material that prevents current from leaking out and causing shocks.
Polarization
The process by which molecules in a dielectric material align their electric dipoles in response to an external electric field, creating an induced electric field within the material.
Example:
When you rub a balloon on your hair, the balloon becomes charged due to polarization of the hair molecules, causing them to stand on end.
Potential difference
The work done per unit charge to move a charge between two points, which decreases across a capacitor when a dielectric is inserted while charge is constant.
Example:
A car battery provides a potential difference of 12 volts, driving current through the car's electrical system.