Electrodynamics & Magnetism 2

4 factors affecting resistance?

Material (direct), length (direct), area (inverse), temperature (direct for metals, inverse for semiconductors).

Formula for Ohm’s Law?

V = I × R.

Series circuit: current?

Same everywhere.

Series circuit: resistance?

Adds (R_total = R₁ + R₂ + …).

Parallel circuit: voltage?

Same across each branch.

Parallel circuit: resistance?

Decreases (1/R_total = 1/R₁ + 1/R₂ + …).

Two sources of current?

Battery, generator.

What does a voltmeter measure?

Voltage (connected in parallel).

What does an ammeter measure?

Current (connected in series).

What is magnetism?

Ability of certain materials to attract iron, cobalt, nickel.

3 types of magnets?

Natural, artificial permanent, electromagnets.

Example of natural magnet?

Earth, lodestone.

Example of artificial permanent magnet?

Refrigerator magnet.

Example of electromagnet?

Motor magnet (current in coil).

3 laws of magnetism?

Polarity (two poles), attraction/repulsion (like repels, unlike attracts), inverse square law (force weakens with distance).

What is a magnetic field?

Zone of influence around a magnet.

What are flux lines?

Magnetic lines of force from north → south.

What makes a magnetic field stronger?

More flux lines per area (flux density).

What is permeability?

How easily material can be magnetized.

What is retentivity?

Ability to stay magnetized.

4 classifications of matter (magnetic)?

Ferromagnetic (strong), paramagnetic (weak), non-magnetic (none), diamagnetic (repelled).

What is electromagnetism?

Relationship between electricity and magnetism.

Oersted’s discovery?

Current-carrying wire produces magnetic field.

Left thumb rule?

Thumb = current direction, fingers = flux direction.

What is a solenoid?

Coil of wire carrying current.

What is an electromagnet?

Solenoid with iron core.

What is electromagnetic induction?

Voltage induced when wire cuts magnetic flux.

3 ways to induce EMF (Electromotive Force)?

Wire moves across flux, flux moves across wire, flux strength changes.

4 factors that affect induced EMF?

Speed, strength of field, angle (best at 90°), number of turns.

Left-hand rule (dynamo rule)?

Index = flux, thumb = motion, middle finger = current.

What is self-induction?

Coil induces voltage in itself (opposes applied current).

What is mutual induction?

AC in one coil induces voltage in another.