Electric Charge and Electric Field Flashcards

Flashcards based on lecture notes about electric charge, electric fields, Coulomb's Law, and related concepts.

What are the earliest documented studies on electricity?

The earliest studies on electricity date back to the ancients, but electricity has only been studied in detail in the past two centuries.

From what Greek word does "electricity" originate?

The word electricity comes from the Greek word elektron, which means "amber."

What did Benjamin Franklin contribute to the study of electric charge?

Benjamin Franklin named the two types of electric charge positive and negative.

What is the law of conservation of electric charge?

The net amount of electric charge produced in any process is zero; no net electric charge can be created or destroyed.

What particles are found in the nucleus of an atom?

The nucleus contains protons, which are positively charged, and neutrons, which have no net electric charge.

What is an ion?

An atom that has lost or gained one or more electrons and has a net positive or negative charge.

How can the charging of a solid object by rubbing be explained?

By the transfer of electrons from one object to the other.

Why is static electricity more noticeable on dry days?

On dry days, static electricity is much more noticeable since the air contains fewer water molecules to allow leakage of charge.

What are conductors?

Materials that allow electric charge to flow freely.

What are insulators?

Materials that do not allow electric charge to flow freely.

What are semiconductors?

Materials that fall into an intermediate category between conductors and insulators.

What are "free electrons" or "conduction electrons"?

Electrons that are bound very loosely and can move about freely within the material of a conductor.

What happens when a positively charged object is brought close to a conductor?

The free electrons in the conductor are attracted by this positively charged object and move quickly toward it.

What is an electroscope?

A device that can be used for detecting charge.

What did Charles Coulomb investigate in the 1780s?

Electric forces using a torsion balance.

What is Coulomb's Law?

The force one small charged object exerts on a second one is proportional to the product of the magnitude of the charge on one, Q₁, times the magnitude of the charge on the other, Q₂, and inversely proportional to the square of the distance r between them

What is the SI unit of charge?

The coulomb (C).

What is the elementary charge?

The charge on one electron, with a magnitude of about 1.602 × 10⁻¹⁹ C, is the smallest charge found in nature, and is often referred to as the elementary charge.

How does Coulomb's law compare to the law of universal gravitation?

Both are inverse square laws, both have a proportionality to a property of each object (mass for gravity, electric charge for electricity), and both act over a distance.

What is "charging by conduction?"

The process where a charged object touches a neutral object, and free electrons in the neutral one are attracted to the positively charged object, giving the second object a net positive charge. Also known as charging by contact.

What is "charging by induction?"

When a charged object is brought near a neutral metal rod, but does not touch it. Although the free electrons of the metal rod do not leave the rod, they still move within the metal toward the external positive charge, leaving a positive charge at the opposite end of the rod.

What circumstances define when an object is said to be "grounded" or "earthed."

When a metal object is connected with a conducting wire to the ground (or a conducting pipe leading into the ground).

What does the constant €₀ represent?

The permittivity of free space.

How can multiple electrical forces be calculated?

If several (or many) charges are present, the net force on any one of them will be the vector sum of the forces due to each of the others.

What is electric field?

An electric field extends outward from every charge and permeates all of space.

State the electric field equation.

Ē = F/q (electric field = Force/charge)

What is an electric dipole?

The combination of two equal charges of opposite sign, +Q and -Q, separated by a distance l.

What is a polar molecule?

A molecule that has a dipole moment, such as the diatomic molecule CO.

In what ways do photocopy machines use electrostatics?

Photocopy machines use electrostatic attraction to print an image via lenses and mirrors that focus an image of the original sheet of paper onto a selenium drum.

In what ways do laser printers use electrostatics?

Laser printers use electrostatic attraction to print an image via computer output used to program the intensity of a laser beam onto the selenium-coated drum.