Ch. 5 - Electrostatics and Magnetism

7% of MCAT Physics content

What is the SI unit of charge?

The coulomb (C).

What is the fundamental unit of charge?

e = 1.60×10⁻¹⁹ C

What charges do protons and electrons have?

Protons have a positive charge, and electrons have a negative charge.

How do opposite and like charges interact?

Opposite charges attract, and like charges repel.

What are conductors?

Materials that allow the free and uniform passage of electrons when charged.

What are insulators?

Materials that resist the movement of charge and have localized areas of charge.

What does Coulomb’s law describe?

The magnitude of the electrostatic force vector between two charges.

How does the force vector from Coulomb’s law behave?

It points along the line connecting the centers of the two charges.

What is an electric field?

A field generated by every charge that can exert forces on other charges.

How are electric field vectors represented?

As field lines radiating outward from positive charges and inward to negative charges.

How do positive and negative test charges move in an electric field?

Positive test charges move along field lines; negative test charges move opposite to them.

What is electric potential energy?

The work required to bring a test charge from infinitely far away to a position near a source charge.

When does electric potential energy increase?

When like charges move closer or opposite charges move farther apart.

When does electric potential energy decrease?

When opposite charges move closer or like charges move farther apart.

What is electric potential?

Electric potential energy per unit charge.

What is potential difference (voltage)?

The change in electric potential when a test charge moves between two positions.

In which direction do positive test charges spontaneously move?

From high potential to low potential.

In which direction do negative test charges spontaneously move?

From low potential to high potential.

What are equipotential lines?

Lines around a charge where all points have the same electric potential.

How are equipotential lines oriented relative to electric field lines?

They are perpendicular.

When is work done between equipotential lines?

When a charge moves between lines, not along the same line.

What is an electric dipole?

Two charges of opposite sign separated by a fixed distance.

What happens to an electric dipole in an external electric field?

It experiences a torque aligning it with the field but no translational motion.

What creates magnetic fields?

Magnets and moving charges.

What is the SI unit for magnetic field?

The tesla (T).

What are diamagnetic materials?

Materials with no unpaired electrons that are slightly repelled by a magnet.

What are paramagnetic materials?

Materials with some unpaired electrons that become weakly magnetic in an external field.

What are ferromagnetic materials?

Materials with unpaired electrons that become strongly magnetic in an external field.

How do magnetic field lines behave in magnets?

They point from the north pole to the south pole.

What shape are magnetic fields around current-carrying wires?

Concentric circles.

When do external magnetic fields exert forces on charges?

When charges move in directions other than parallel or antiparallel to the field.

What motion do point charges experience in a uniform magnetic field?

Uniform circular motion due to the centripetal magnetic force.

How is the direction of the magnetic force determined?

Using the right-hand rule.

What is the Lorentz force?

The sum of electrostatic and magnetic forces acting on a body.