Unit 4: Electricity, magnetism, and electromagnetism

What is the primary function of the x-ray tube?

To convert electric energy into electromagnetic energy (x-rays)

Electrostatics

the study of stationary electric charges

Electrons

the smallest unit of negative electrical charge

Protons

the smallest unit of positive electrical charge

Electrons and protons have the same magnitude (true/false?)

True

Electrons and protons have the same charge (true/false?)

False

When discussing electric charge, you are mainly discussing 

electrons

Why are electrons more important when talking about electric charge than protons?

Because electrons travel freely from outermost atomic shell and protons are bound in the nucleus and do not travel freely.

An object is electrified if it has

too many or too few electrons

How can something be electrified

By contact, friction, or induction

The Earth is called an

electric ground

Why is Earth called an electric ground?

Because it is always able to accept electric charges (Earth can take up almost infinite amount of electrons)

What does Coulomb measure?

number of electrons

1C =

6.3×10^18 electron charges

What does Ampere measure

The flow of one coulomb per second

What is the 1st Electrostatic law?

Unlike charges attract; like charges repel

the force of attraction, or repulsion, between charges is called

Electrostatic force

Electrostatic force is similar to

magnetism

What is the 2nd Electrostatic Law?

Coulomb’s Law

Coulomb’s law

The electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance between them. (very strong when close together, decreases rapidly with distance)

Coulomb’s law is similar to the

inverse square law

According to Coulomb’s law, attraction/repulsion increases/decreases

by the square of the distance

F= K (QaQb/d²) 

Coulomb’s equation

What is F in Coulomb’s equation?

electrostatic force (newton)

What is Qa and Qb in Coulomb’s equation?

electrostatic charges (coulomb)

what is d in coulomb’s equation?

distance

What is k in coulomb’s equation?

a constant of proportionality

What is the 3rd electrostatic law?

Electric charge distribution is uniform throughout, or on the surface.

according to the third electrostatic law, electrons are ________ ______ on the outer surface of copper wire

evenly distributed

What is the 4th electrostatic law?

Electric charge of a conductor is concentrated along the sharpest curvature of the surface.

A system that has potential energy has

the ability to do work when the energy is released

Electric charges have _____ energy

potential

An example of electric charge potential energy is: like charges that are close together

can do work when they fly apart

Electrical potential is called

voltage

What is the unit for electrical potential?

Volt (V)

Increased voltage =

increased potential to do work

What is the standard voltage in the US?

110V

What is the standard voltage in places other than the US?

220V or >

Voltage in the US is not

constant/stable

When lots of people are using electricity voltage dips

Electrodynamics

Study of electric charges in motion

Electric current/electricity

electric potential applied to copper wire causes electrons to move along the wire

voltage = the _____ in a water hose, Current= the _____ in a water hose

pressure, amount of water

Benjamin Franklin assumed _____ electrical charges were conducted

positive

Because of Franklin, electric current is considered _________ of electron flow

opposite

Physicists study

electron flow

An insultor

confines the electron flow to the copper wire

What are common household insulators?

plastic or rubber

What is the most common material used for household wire?

copper

What are the four electric states of matter?

superconductor, conductor, semiconductor, and insulator

What is a superconductor?

A material that is very cold and allows current without the presence of voltage.

Does not obey Ohm’s law

Ex: Niobium, Titanium

What is a conductor?

any substance through which electrons flow easily

Requires voltage (electric potential)

Obeys Ohm’s law

Ex: Copper, Aluminum, Water (because of impurities)

What is a semiconductor?

A material that can behave as a conductor or an insulator

Computer technology (binary code - 1=allows electron flow, 0=does not allow electron flow)

Ex: Silicon, Germanium

What is an insulator?

A material that does not allow electron flow

Extremely high resistance

Ex: rubber, glass

Electric circuit

A conductor with controlled resistance and made into a closed path

What unit is electric current measured in?

Amperes (A)

1 ampere (A) =

an electric charge of 1C flowing through a conductor each second

Increased resistance causes _____ electric current

reduced

Electric potential is measured in

volts (V)

Electric resistance is measured in 

ohms (n<weird symbol)

The voltage across the total circuit, or any portion of the circuit, is equal to the current times the resistance

Ohm’s law

Ohm’s equation

V=IR

In ohm’s equation, V=

electric potential in volts

In Ohm’s equation, R=

electric resistance in ohms

In Ohm’s equation, I=

electric current in amperes

resistor

inhibits flow of electrons

Battery

provides electric potential

Capacitor

momentarily stores electric charge

Transformer

increases or decreases voltage by fixed amount (AC only)

Diode

allows electrons to flow in only one direction

Series circuit

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

electrons come in one side, go in a loop, and go back in.

According to the series circuit rules, the total resistance is (-)

equal to the sum of the indicidual resistances

According to the series circuit rules, the current through each circuit element is (-)

the same and is equal to the total circuit current

According to the series circuit rules, the sum of the voltages across each circuit element is (-)

equal to the total circuit voltage

Parallel circuit

elements are connected at their ends rather than lying in a line along a conductor

Christmas lights that don’t all go out when one bulb goes out.

parallel circuit

Christmas lights that all go out when one bulb goes out

Series circuit

According to parallel circuit rules, the sum of the currents through each circuit element is (-)

equal to the total circuit current

according to parallel circuit rules, the voltage across each circuit elements is (-)

the same and is equal to the total circuit voltage

According to the parallel circuit rules, the total resistance is (-)

the inverse of the sum of the reciprocals of each individual resistance

Direct current (DC)

electrons flow in one direction only

Alternating Current (AC)

electrons oscillate back and forth

What is the standard household AC in the US?

60Hz

What is the standard household AC in the rest of the world (not the US)?

50Hz

What unit is used to measure AC?

Hz 

What unit is used to measure DC

voltage

Why is AC measured in Hz (frequency) and DC in volts?

DC fluctuates while AC is constant (constant frequency of 60Hz in the US)

Oscillation of AC is

sinusoidal

Each oscillation of AC is _____ of a second

1/60 (120 pulses per second)

Electric power is measured in

Watts (W)

How much power do most common appliances use?

500-1500W

How much power do light bulbs use?

30-150W

1W =

1A of current flowing through an electric potential of 1V

Power(W) = *()=units

voltage (V) x current (A)

Voltage (V)=    *()=abbreviations

current (I) x resistance (R)

P=

IV OR I²R

Fe3O4

magnetite/iron oxide

Magnetite was discovered around _____ near _____

1000 B.C. ; the village of magnesia (what is now western turkey)

Magnetite, when suspended by a string, it would rotate back and forth. In this scenario it was called

lodestone or leading stone

Why was it called lodestone or leading stone?

because people believed it led them to water

Any charged particle in motion creates

a magnetic field