Electric Charge, Fields, and Electromagnetic Principles: A Comprehensive Physics Review

What is electric charge?

A fundamental property of matter that causes electric forces between particles.

What does conservation of charge mean?

Electric charge cannot be created or destroyed, only transferred.

What are the two types of electric charge?

Positive and negative.

Which subatomic particle is responsible for most electrical phenomena?

The electron.

Why are electrons mobile in solids but protons are not?

Electrons are much lighter and not bound in the atomic nucleus.

What happens between like charges?

They repel each other.

What happens between opposite charges?

They attract each other.

What determines an element's identity?

The number of protons in its nucleus.

What law governs electric forces between charges?

Coulomb's law.

What is Coulomb's law equation?

F = k(q1q2 / r^2)

How does electric force change with distance?

It decreases with the square of the distance.

Why is electric force much stronger than gravity?

Electric interactions are intrinsically stronger than gravitational ones.

What is an electric field?

A vector field that describes the force a charge would experience at a point.

Why are electric fields considered more fundamental than forces?

Fields exist even when no test charge is present.

How is electric field direction defined?

The direction a positive test charge would accelerate.

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

Radially outward.

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

Radially inward.

What is the electric field equation for a point charge?

E = k(q / r^2)

What is the force on a charge in an electric field?

F = qE

When is Gauss's law most useful?

For symmetric charge distributions like spheres or planes.

What is static electricity?

The buildup of excess charge on an object.

Why can charged objects attract neutral ones?

Electric polarization redistributes charges inside the neutral object.

Why is static electricity reduced in humid air?

Moisture allows excess charge to dissipate.

What distinguishes conductors from insulators?

Conductors have mobile charge carriers; insulators do not.

What is the electric field inside a conductor at equilibrium?

Zero.

What is electric potential energy?

Energy due to a charge's position in an electric field.

What is voltage?

Electric potential energy per unit charge.

What is the unit of voltage?

Volts, equivalent to joules per coulomb.

What is the relationship between voltage and energy?

ΔE = qV

What is the function of a battery?

To maintain a constant voltage.

Do batteries supply charge?

No, they supply energy.

What is electric current?

The flow of charge per unit time.

What is the unit of current?

Ampere.

What actually moves in metal wires?

Electrons drifting slowly through the conductor.

What causes electrons to move through a circuit?

An electric field established by voltage.

What is Ohm's law?

I = V / R

What is resistance?

Opposition to the flow of electric current.

What is the unit of resistance?

Ohms.

What is electrical power?

The rate at which electrical energy is transferred.

What is the power equation?

P = IV

Why do resistors heat up?

Electrical energy is converted into thermal energy.

In a series circuit, what stays the same?

Current.

What is the total resistance in series circuits?

Resistances add directly.

In a parallel circuit, what stays the same?

Voltage.

What is the total resistance in parallel circuits?

The reciprocal sum of resistances.

Why are household circuits wired in parallel?

Devices operate independently at full voltage.

What is a capacitor?

Two conductors separated by an insulator.

What does a capacitor store?

Energy in an electric field.

Why do capacitors block DC but pass AC?

They respond only to changing electric fields.

What creates magnetic fields?

Moving electric charges.

Do magnetic fields act on stationary charges?

No.

What is the fundamental unit of magnetism?

A magnetic dipole.

Why do magnetic monopoles not exist?

Magnetic fields arise from paired north and south poles.

Why aren't all materials magnetic?

Atomic magnetic moments usually cancel out.

What is ferromagnetism?

A property where atomic magnetic moments align permanently.

What is paramagnetism?

Temporary magnetization in the presence of a field.

What is a magnetic field?

A vector field created by moving charges.

What is magnetic force?

A force that deflects moving charges without changing their speed.

What is the magnetic force equation?

F = qvB

What is the direction of magnetic force?

Perpendicular to both velocity and magnetic field.

What motion results from magnetic force alone?

Circular motion.

Who discovered the magnetic effect of current?

Hans Christian Oersted.

What is a solenoid?

A coil of wire that produces a magnetic field when current flows.

What is electromagnetic induction?

Voltage generated by a changing magnetic field.

What is Faraday's law equation?

V = −N(ΔΦB / Δt)

What is the conceptual meaning of Faraday's law?

Changing magnetic flux induces current.

What does Lenz's law state?

Induced current opposes the change that created it.

What is the difference between a generator and a motor?

Generators convert motion to electricity; motors convert electricity to motion.

Why do transformers require AC?

Only changing magnetic fields induce voltage.

What is an electromagnetic wave?

Oscillating electric and magnetic fields that propagate through space.

Do electromagnetic waves need a medium?

No.

What is the speed of light in vacuum?

3 × 10^8 m/s.

What is the wave speed equation?

v = λf

What determines electromagnetic wave energy?

Frequency.

What determines intensity or brightness?

Amplitude.

What is the order of the electromagnetic spectrum from low to high frequency?

Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.

What is the visible light wavelength range?

Approximately 400-700 nm.

What does polarization describe?

The orientation of the electric field.

How do polarizing sunglasses work?

They absorb light polarized in one direction.

What is the core principle of special relativity?

The speed of light is constant for all observers.

What is time dilation?

Moving clocks run slower relative to stationary observers.

Why is magnetism considered relativistic?

It arises from electric forces viewed in different reference frames.

What unifies electricity, magnetism, and light?

The electromagnetic force.