132 Unit 2

Law of repulsion-attraction

Like charges repel; unlike charges attract.

The inverse square law.

The force between two charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them. As a charged object gets further away, the influencing charge decreases because of the increased area it affects.

Law of distribution.

Charges reside on the external surfaces of conductors and equally throughout nonconductor. This law is a result of the effect of the repulsion- attraction law, as electrons, all with negative charges, attempt to repel each other as much as possible.

Law of concentration.

The greatest concentration of charge will be on the surface where the curvature is sharpest. If enough electrons congregate, they can induce ionization of the surrounding air and even discharge to the nearest point of lower concentration.

Law of movement

Only negative charges move along solid conductors. Because the positive charges, the protons, are tightly bound inside the atomic nuclear field, only the electrons, which exist outside the nucleus, are easily moved along conductors.

Electrostatics

the study of the distribution of fixed charges, or electrons that are at rest.

Like charges ___?

Repel

Nearly all discussion of electricity deals with the movement of?

Negative charges

Coulomb’ s law

inverse square law

Ground potential

The electrical potential of the Earth, used as a reference point of zero

Grounding’s primary purpose

Provide a safe path to earth for fault current

Grounding sends electrons

To the earth

Electrification

the action or process of charging something with electricity.

Electrification by friction

occurs when one object is rubbed against another and, due to differences in the number of electrons available on each, electrons travel from one to the other.

Electrification by contact

occurs when two objects touch, permitting electrons to move from one to the other. This process is a simple equalization of charges, with both objects having similar charges after the contact.

Electrification by induction

Induction is the process of electrical fields acting on one another without contact.

Positively charges mean it has

Less electrons

Negatively charge means it has

An excess in electrons

Electrodynamics

the study of the distribution of moving charges

What best describes an insulator

Inhibits electrons from moving

What best describes conductors

Easily allows electrons to flow

What best describes semiconductors

Has the ability to conduct under certain conditions and inhibit under others

Examples of conductors

Metals such as copper and aluminum

Examples of insulators

Plastic, rubber, and glass

Examples of semiconductors

Silicon, and germanium.

Electrical circuit definition

A pathway that permits electrons to move in a complete circle from their source

Electrons always move from

Negative to positive

Electrical circuits must always have

Conducting pathway

Closed pathway

Potential difference

Current Unit of measurement

Ampere or amp

Current Abriviation

A

Current Definition

The quantity, or number, of electrons flowing

Potential Difference unit of measurement

Volt

Potential Difference abbreviation

V

Potential Difference definition

the force or strength of electron flow

Resistance unit of measurement

Ohm

Resistance abbreviation

Ω

Resistance definition

The amount of opposition to the current in the circuit

Electrons flow from

From negative to positive

Area of abundance to area of defiencency

According to laws of electrostatics two objects with opposite charges will tend to

Attract each other

A conductor current consists of a flow of moving

Electrons

Direct current

When all electrons move in the same direction

Alternating current

When electrons move first in one direction and then reverse and move in the opposite direction.

You do not need current flowing in order to have

Potential difference

You need potential difference in order to have

Current flowing

1A=1C/s=

6.24×10^18e-

mA sets the

current/ quantity of electrons

300 mA =

.3 A

kVp is

the quality/energy of the photon

Current is represented as ___ in a formula

I

I=

V/R

V=

IR

Resistance is represented by ___ in a formula

R

Voltage is represented by ___ in a formula

V

Alternating current’s electrons change

direction during current flow

Transformers will only operate off of

Alternating current

Direct currents poles are always the same, so the electrons are always

travelling in one direction

Direct current never

goes to the negative cycle

Insulating material effect on resistance

Increase

Increased temperatures effect on resistance

Increase

Decreased length of a conductor effect on resistance

Decrease

Decreased cross-sectional area of a conductor effect on resistance

Increase

What did Hans Oersted conclude via is compass experiment

Charged particles in motion creates a magnetic field

Faraday discovered

A change in magnetic field creates a current

Faraday is always the

First law of electromagnetism

Self-induction has ____ coil/conductor

One

Self-Induction induces voltage____

in itself

Self-induction magnetic field links the

Same coil

Mutual induction has ____ coil/conductor

two

Mutual Induction coil induces voltage

in another coil

Mutual induction magnetic field links

a second coil

What is the purpose of a generator

Change mechanical into electrical energy

Transformer purpose

Used to change voltage

How do transformers work

Alters electrical current by changing voltage

Alternating current causes the magnetic field to

Expand and contract

The primary coil is

supplied with electrical current

The coil of wire in a transformer delivered with the alternating current is called the

Primary coil

An increase in turns in the secondary coil would occur in a

step-up transformer

A decrease in turns in the secondary coil would occur in a

step-down tansformer

A step-up transformer will ___ voltage

increase

A step-down transformer will ___ voltage

decrease

A step-up transformer increases voltage and ___ current

decreases

A step-down transformer decreases voltage and ____ current

increases

The transformer law for voltage is

( Vs/Vp)=(Ns/Np)

The transformer law for current is Is/Ip=Vp/Vs and Is/Ip=Np/Ns

Is/Ip=Vp/Vs and Is/Ip=Np/Ns

The transformer law for voltage is ____ proportional

directly

The transformer law for current is ____ proportional

inversely