Acadeca Science Section I Electricity - Charged Particles (Pg.6-27)

A set of practice flashcards covering key concepts from the lecture notes on electricity, atoms, charges, fields, and related laws.

What term did William Gilbert use in 1600 for the mysterious force revealed by rubbing amber, and what is the origin of the word 'electric'?

The electric force; from the Greek word for amber, elektron.

Name the four classical elements that Western thought believed matter was made of.

Earth, air, fire, and water.

Why are hydrogen and oxygen not considered truly fundamental elements, according to the notes?

Because elements are composed of atoms, which themselves are made of smaller particles (protons, neutrons, electrons); even H and O are not ultimately fundamental.

What does the Greek word 'atom' mean, and what was the historical debate about divisibility?

Atom means indivisible; historically debated whether matter could be cut into ever-smaller pieces or was infinitely divisible.

What is Franklin’s key contribution to our understanding of electrical charge?

Charge is conserved: it cannot be created or destroyed, only moved between objects.

What are the three basic particle types in an atom and where are they located?

Protons and neutrons in the nucleus; electrons orbiting the nucleus.

Which subatomic particles carry electric charge and what are their charges?

Protons (positive), electrons (negative); neutrons are electrically neutral.

Which particle is primarily involved in electricity, and why?

Electrons; they move and carry charge; protons are much more massive.

What is Coulomb’s law and its equation?

FE = k q1 q2 / r^2; the electric force between two charges.

What is the value of the Coulomb constant k?

k = 8.99 × 10^9 N m^2 / C^2.

State Newton’s law of gravitation as given in the notes and describe the inverse-square relationship.

Fg = G m1 m2 / r^2; gravity follows an inverse-square law with distance.

How does the electric force between two electrons compare in magnitude to their gravitational force?

Electric force is about 10^40 times stronger than gravity between two electrons.

What is an electric field and how does FE = qE relate to force?

An electric field E conveys force per unit charge; FE = qE; direction depends on the sign of q.

What happens to the electric field at a point exactly midway between two equal positive charges?

The fields cancel, giving a net electric field of zero at that point.

What is an electric dipole?

Two equal and opposite charges separated by a distance, creating a characteristic field.

What is Gauss’s law and its basic equation?

ΦE = Q_enclosed / ε0; the electric flux through a closed surface equals the enclosed charge divided by ε0.

What is ε0 and how does it relate to the Coulomb constant k?

ε0 is the permittivity of free space; ε0 = 1/(4πk).

What is the electric field due to an infinite sheet of charge?

E = σ / (2ε0); the field is uniform and independent of position.

Differentiate scalar and vector fields with examples from the notes.

Scalar fields have magnitude only (e.g., temperature, mass); vector fields have both magnitude and direction (e.g., velocity, electric field).

Which geometric surface is commonly used in Gauss’s law for a sheet of charge, and why?

A cylinder (Gaussian surface) is used because the side flux is zero and the top/bottom have equal flux.

What is static electricity as described in the notes?

Charge buildup on everyday objects due to rubbing or contact, often leading to shocks.

What is electrical polarization and how does it allow a neutral object to interact with a charged object?

External electric fields separate charges within a neutral object, creating a dipole and net attraction.

What is a Faraday cage and its practical implication?

A conducting enclosure that shields the interior from external electric fields.

What is a Van de Graaff generator used for?

A device that uses a belt to move electrons to a high-voltage metal sphere, generating static charge.

How does polarization explain a balloon sticking to a wall?

The balloon’s negative charge polarizes wall atoms, creating a net attraction despite the wall being neutral.

Describe the difference between conductors and insulators with examples.

Conductors (e.g., metals like copper) allow charge to flow; insulators (e.g., plastic) do not.

What happens to a conductor’s interior electric field when it is charged?

The interior electric field is zero; charges reside on the surface.

What is the direction of the electric field around a positive charge vs a negative charge?

Around a positive charge the field points outward; around a negative charge it points inward.

What is the magnitude and sign of the elementary charge on a proton and electron?

Proton: +1.7 × 10^-19 C; Electron: -1.7 × 10^-19 C; the charges are equal in magnitude and opposite in sign.

Why is gravity the dominant force at large scales if both gravity and electric charge exist in everyday objects?

Most objects are electrically neutral overall, so there is little net electric force externally; gravity acts on mass and cannot be canceled.

What two quantities determine the gravitational force according to Newton’s law used in the notes?

Masses m1 and m2 and the distance r between them (F = G m1 m2 / r^2).

What is the relationship between distance and electric field strength for a point charge vs a sheet of charge?

Point charge: E ∝ 1/r^2; sheet of charge: E is constant (independent of position, under ideal conditions).

What are the masses of the proton and electron as given in the notes?

Proton ≈ 1.7 × 10^-27 kg; Electron ≈ 9.1 × 10^-31 kg.

What is the traditional form of Newton’s third law as described in the notes?

Every action has an equal and opposite reaction.

How do symmetry and Gauss’s law help simplify calculating electric fields for extended objects?

Symmetry allows us to avoid computing every particle’s field by considering the net effect; e.g., sheet or spherical symmetry.