Unit 3: Electricity Magnetism and Electromagnetism

Smallest unit of electrical charge

electron

One coulomb is how many electrons?

6.3 x 10^18

Electrostatics

The study of electric charges at rest

Electrification

Too few or too many electrons

Methods of Electrification

friction, contact, induction

Negative charges pull _____, positive charges push ______

Inward, Outward

1st Law of Electrostatics

like charges repel, unlike charges attract

2nd Law of Electrostatics

Electrons travel outside of a conductor(wire)

3rd Law of Electrostatics

Electrical charges are concentrated on the sharpest curvature of a conductor.

4th Law of Electrostatics

Electrostatic force is directly proportional to the product of the charges and are inversely proportional to the square of the distance.

Electrodynamics

The study of electric charges in motion

Conductor

A material that allows heat and electricity to pass through it.

Insulator

A material that does not allow heat or electrons to move through it easily.

Semiconductor

A substance that can conduct electricity under some conditions

Superconductor

a material that has almost zero resistance when it is cooled to low temperatures

Current

Measured in amperes (A)

Potential Differences- volts(V)

EMF (Electro Motor Force)

Resistances(R)

Measured in Ohms

Length of the Wire

Longer the wire, more resistance

Cross-section of the wire

Thinner the wire, more resistance

Material the wire is composed of

Gold is a better material than wire

Temperature of the wire

Higher temperature has more resistance

Ohm's Law

V = I(R)

Power (Measured in Watts)

P = I(V) or P = I^2(R)

Open switch symbol

The circuit is switched OFF

Closed Switch

The circuit switch is ON

Transformer

A device that increases or decreases the voltage of alternating current

Resistor

An electrical device that resists the flow of electrical current

Diode

A device that permits current to flow through it in only one direction.

Battery

DC supply of voltage and current, usually made of many cells

Voltmeter

A device used to measure potential difference, must be put in parallel

Anmeter

A device used to measure the current flowing through a circuit, must be in a series

Ferromagnetic

Substances that can become magnetized; iron, nickel & cobalt. Their atoms will form magnetic domains.

Paramagnetic

Slightly magnetic material

Diamagnetic

Material that cannot be magnetized

Susceptibility

The degree to which a material can be magnetized

Retentivity

the ability of a material to stay magnetized

Magnetic Flux Lines

Parallel lines of force that always go from the north pole to the south pole in a magnet, and surround a DC current-carrying wire.

Strongest point of magnetic flux is __ ___ _____?

At the poles

Electromagnetism

Acts like a magnet, but it's magnetic force is induced by electricity.

Oersted

magnetic field surrounds a moving electrical current

Faraday (1st Law)

current is induced by moving magnetic field

Helix

A coil of wire

Solenoid

a coil of wire with an electric current in it

Lenz Law (2nd law of electromagnetism)

induced current flows in the opposite direction of the applied current (self induction)

Mutual Induction

inducing current flow in a secondary coil by varying the current flow through a primary coil

Generator: _____ to ______ energy

Mechanical, electrical

Motor: _______ to ______ energy

Electrical, mechanical

Induction Motor

Powers the rotating anode of an X-ray tube

Self-induction

Utilizes one could which acts as a primary and secondary coil

Mutual induction transformer

Changes voltage and current in the secondary coil is caused by a change in the voltage/current of the primary coil

Open Core

-iron core is inserted

-leakage flux

-least efficient

Closed Core

-continuous path

-minimal leakage

-core is laminated

Shell Core

-most advanced

-wiring is insulated

-common in modern x-ray systems

-most efficient