Electric Charges, Forces, and Fields: Key Concepts and Laws

What happens when two objects rubbed with the same material are brought together?

They repel.

What happens between a rubbed object and the material used to rub it?

They attract.

What are the two types of electric charge?

Positive (+) and negative (−).

What is the rule for electric charges?

Opposites attract and likes repel.

What particles are positively charged?

Protons.

What particles are negatively charged?

Electrons.

What particles have no charge?

Neutrons.

When is an atom neutral?

When the number of protons equals the number of electrons.

What happens if an atom loses electrons?

It becomes positively charged.

What happens if an atom gains electrons?

It becomes negatively charged.

During charging by rubbing, which particles move?

Electrons only.

What law states charge cannot be created or destroyed?

Conservation of charge.

What is an insulator?

A material that does not allow charges to move easily.

Give examples of insulators.

Glass, wood, plastic, rubber, dry air.

What is a conductor?

A material that allows charges to move freely.

Give examples of conductors.

Metals, water, human body, humid air.

What is charging by conduction?

Charging by touching a charged object to a neutral object.

What is charging by induction?

Charging without direct contact.

What is grounding?

Neutralizing an object by connecting it to Earth.

What symbol represents charge?

q

What is the SI unit of charge?

Coulomb (C)

What is an electric field?

A region around a charge that exerts forces on other charges.

Are electric forces contact forces?

No, they act at a distance.

How do electric field lines behave around positive charges?

They point outward.

How do electric field lines behave around negative charges?

They point inward.

What direction do positive charges move in an electric field?

Same direction as field lines.

What direction do negative charges move in an electric field?

Opposite the field lines.

What is the equation relating force and electric field?

F = qE

What is the unit for electric field strength?

Newtons per Coulomb (N/C)

What does Coulomb's Law calculate?

The electric force between two charges.

What is Coulomb's Law equation?

F = k(q₁q₂)/r²

What is the value of Coulomb's constant (k)?

9 × 10⁹ N·m²/C²

What variable represents distance in Coulomb's Law?

r

How does doubling one charge affect force?

The force doubles.

How does doubling both charges affect force?

The force becomes four times larger.

How does doubling distance affect force?

The force becomes one-fourth as large.

Why is Coulomb's Law called an inverse-square law?

Force changes with 1/r².

Can electric force attract and repel?

Yes.

Can gravity repel?

No, gravity only attracts.

Which is stronger in atoms: electric force or gravity?

Electric force.

What is the principle of superposition?

Total force equals the vector sum of all individual forces.

What law explains equal and opposite forces between charges?

Newton's Third Law.

What is electric potential difference?

Energy difference that causes charge flow.

What variable represents voltage?

V

What unit measures voltage?

Volts (V)

Positive charges move from ____ potential to ____ potential.

High to low.

Negative charges move from ____ potential to ____ potential.

Low to high.

What creates potential difference in a circuit?

A battery.

What is electric current?

The flow rate of charge.

What variable represents current?

I

What unit measures current?

Amperes (A)

What is resistance?

Opposition to current flow.

What variable represents resistance?

R

What unit measures resistance?

Ohms (Ω)

State Ohm's Law.

V = IR

How are components arranged in series circuits?

One after another in a single path.

What happens to current in series circuits?

It stays the same everywhere.

What happens to voltage in series circuits?

It changes across components.

How do you find total resistance in series?

Add resistances directly.

Formula for equivalent resistance in series?

Req = R₁ + R₂ + R₃

Is equivalent resistance in series larger or smaller than component resistors?

Larger.

How are components arranged in parallel circuits?

In branches.

What happens to voltage in parallel circuits?

It stays the same in every branch.

What happens to current in parallel circuits?

It splits among branches.

How is total current found in parallel?

Add branch currents.

Formula for total current in parallel?

IT = I₁ + I₂ + I₃

How do resistors combine in parallel?

Add reciprocals.

Formula for equivalent resistance in parallel?

1/Req = 1/R₁ + 1/R₂ + 1/R₃

Is equivalent resistance in parallel larger or smaller than component resistors?

Smaller.

What happens to equivalent resistance when more parallel branches are added?

It decreases.