Basic Circuitry

Matter

- has a mass and energy equivalence

- may also have electric charge

Electric charge

- comes in discrete units that are:

- Positive ( + ) or proton

- Negative ( - ) or electron

- is associated with an electron and proton have the same magnitude but opposite direction

X-ray unit

- purpose is to convert electric energy into electric energy

X-ray beam

- is an Electromagnetic Energy

History

Electricity

- comes from the Greek elektron which means “amber”

- the “amber effect” is what we call static electricity

Electrostatics - is the study of stationary electric charge

Matter - are made up of atoms

Electrons - often are free to move from the outermost shell of the atom

Protons - are fixed inside the nucleus or do not free to move

Electrification

- can be created by friction, induction or contact (FIC)

- is due to the movement of negative electric charge

An object is said to be electrified if it has too few or too many electrons.

Ground

- electrically neutral object which acts as a reservoir for electric charges

Charge Concepts

- opposite charges attract, like charges repel

- Unit: C, Coulomb

- 1 C = 6 X 10^18 electron charges

- 1 A= 1 C/s

- mAs = mC

A radiograph is made at 40 mAs. calculate the total number of electrons that will flow from cathode to anode.

Given: mAs = 40

- 1 C = 6 X 10^18 electron charges

- 1 A= 1 C/s

- mAs = mC

- e- = ?

Electrification

- outer shell electrons of some type of atoms are loosely bound and can be removed easily

- removal of these electrons electrifies the substances from which they were removed and results in Static Electricity

Electric Force

- also known as the Coulomb’s Law

- using a torsion balance, Coulomb found that:

- electric force between two charges is proportional to the product of two charges

- electric force between two charges are inversely proportional to the square of distance between two charges

Electrostatic Laws

1. Electric Field

- electric field points outward from a positive charge

- electric field points toward from a negative charge

- uncharged particles do not have an electric field

2. Electric Charges

- like charges repel and unlike charges attract

3. Electrostatic force (Coulomb’s Law)

- is directly proportional to the product of electrostatic charges

- is inversely proportional to the square of distance between them

4. Electric Charge Distribution

- non-conductor – uniform

- copper wire – outer surface

- sharpest point or curve – concentrated

5. Electric Potential

- a system that possesses potential energy is a system with stored energy

- such a system has the ability to do work when this energy is released

Electrostatic Laws (Page 15)

Electric charge

- have potential energy

- can do work when they are positioned close to each other

Electric potential

- is sometimes called voltage

- 1 volt (V)= 1 J/C

“The higher the voltage, the greater is the potential to do work.”

Electric Field

- electric force is a field force

- it applies force without touching (like the gravitational force)

In region around a charged object, an Electric Field is said to exist

Electostatic Force

- is the repulsion or attraction between charges due to electric field

Electric Charge Distribution

- electric charges are uniformly distributed throughout the object or on its surface

Electric Charge Concentration

- electric charge of a conductor is concentrated along the sharpest curvature of its surface

Electrodynamics

- study of charges in motion

- also known as Electricity or Electric Current

Flow of Electrons = Electric Current

Flow of Electrons

- is opposite to the direction of current

- is easy through conductors

Four States of Electrical Matter

• Superconductor: Niobium and Titanium

• Conductor: Copper and Aluminum

• Semiconductor: Silicon and Germanium

• Insulator: Rubber and Glass

Four States of Electrical Matter

Insulators

- impede the flow of electrons

- extremely high resistance

- necessary with high voltage

Semiconductors

- do both conductor and insulator

- basis for computers

Conductors

- variable resistance

- obeys the Ohm’s law

- requires a voltage

Superconductivity

- some material display no resistance below a critical temperature

Electric Circuits

- electrons flow along outer surface of wire

- is well defined when the path is closed and resistance can be controlled

Electric current

- reducing it results in an increasing electric resistance

- is measured in amperes (A)

1 A = 1 C (electric charge) flowing through a conductor per second

Electric potential - is measured in volts (V)

Electric resistance - is measured in Ohms (Ω)

Ohm’s Law

- voltage (V) across total circuit or any portion of circuit is equal to the current (I) times the resistance (R).

- V = IR

Electric Circuits

• Basic Types:

• Series Circuit

• Parallel Circuit

Series Circuit

- all circuit elements are connected in a line along the same conductor

Rules of Series Circuit

1. Total resistance is equal to sum of individual resistances.

2. Current through each circuit element is the same and is equal to the total circuit current.

3. Sum of the voltages across each circuit element is equal to the total circuit voltage.

Parallel Circuit

- contains elements that are connected at their ends rather than lying in a line along the conductor

Rules of Parallel Circuit

1. Sum of the currents through each circuit element is equal to the total circuit element.

2. Voltage across each circuit element is the same and is equal to the total circuit voltage.

3. Total resistance is inverse of the sum of reciprocals of each individual resistance.