Unit 2: Engineering Fundamentals Part Three Chapters 11 and 12

Temperature is…

One of the seven fundamental or base dimensions that we use to properly express what we know of our world.

Base SI Unit For Temp

Kelvin (K)

Kelvin (K)

Unit of thermodynamic temperature

Temperature provides a measure of…

Molecular activity and the internal energy of an object.

The molecules of a substance at a high temperature…

Are more active than at a lower temperature.

Thermometers

Are based on thermal expansion or contraction of a fluid, such as alcohol, or a liquid mercury.

Mercury thermometer

Is a temperature sensor that works on the principle of expansion or contraction of mercury when its temperature is changed.

What temp does water freeze?

0 * C, 32 * F

What temp does water boil?

100 * C, 212 * F

Celsuis to Fahrenheit Formula

C = (F - 32) divided by 1.8

Fahrenheit to Celsius Formula

F = (C x 1.8) + 32

Both Celsius and Fahrenheit scales are…

Arbitrarily defined.

Kelvin and Rankine scales…

Are absolute scales based on the behavior of an ideal gas

The ideal gas law Definition

Gives the relationship between the pressure of the gas, its volume, and its temperature

Ideal Gas Law Formual

PV = mRT

Heat transfer (Thermal energy transfer)

A form of energy transfer that occurs between bodies of different temperatures.

Heat always flows from a high-temperature region to a…

Low-temperature region.

Temperature measures…

the average kinetic energy of particles in a substance, indicating how hot or cold it is.

Heat measures…

is the total thermal energy transferred between objects due to a temperature difference, always flowing from a hotter object to a colder one.

British thermal unit

Btu

Calorie

Amount of heat required to raise the temperature of 1 gram of water by 1 * C

Conduction

Mode of heat transfer that occurs when a temperature difference (gradient) exists in a medium.

Fourier’s Law

The rate of heat transfer through a material is proportional to the temperature difference

Convection

Mode of heat transfer that occurs when a fluid in motion comes into contact with a surface whose
temperature differs from the moving fluid.

Newton’s Law of Cooling

For both forced and free convection situations, it is the overall heat transfer rate between the fluid and the surface.

The higher the value of R…

The more resistance to heat flow to or from the surrounding fluid.

Stefan-Boltzmann Law

The amount of radiant energy omitted by a surface

Metabolic Rate

The rate of conversion of chemical to thermal energy within a person’s body.

Unit of metabolic rate:

Met. 1 met = 58.2 W/m2

When a fuel is burned, whether it is gas, oil, etc.,…

Thermal Energy is released.

Thermal Expansion

as the temperature of the material is increased, the material will expand – increase inlength – and if the temperature of the material is decreased, it will contract – decrease in length.

Specific heat

Provides a quantitative way to show how much thermal energy is required to raise the temperature of a 1 kg mass of a material by 1* C

What is the physical quantity that quantifies or provides a measure of how active molecules are on a microscopic level?

Temperature

A temperature-measuring device that consists of two dissimilar metals

Thermocouple

A temperature-measuring device composed of a semiconductor material

thermistor

Which of the following temperature scales is known as an absolute scale?

Kelvin

A 1° temperature difference in Celsius is equal to a 1° temperature difference in Fahrenheit.

False

When you touch a hot stove with your finger you get burned by the heat transferred to your finger. What mode of heat transfer is responsible for this?

Conduction

If you stay out too long at the beach you may get a sunburn as a result of too much heat being transferred to your skin. What mode of heat transfer is responsible for this?

Radiation

In general, as the temperature of a material is increased, the material's length will do what?

Increase

Electric Current as a Fundamental Dimension

Ampere (A)

Basic law of electric charges

Unlike charges attract each other while like charges repel.

Unit of charge

coulomb (C)

One coulomb (C) =

The amount of charge that passes a point in a wire in 1 second when a current of 1 ampere is flowing through the wire.

The electric force exerted by one point charge on another is…

• proportional to the magnitude of each
  charge

• inversely proportional to the square of the
  distance between the point charges

The electric force is…

attractive if the charges have opposite signs
repulsive if the charges have the same sign

Electric force between two points is given by

Coulomb’s law

Electric charge is…

Is conserved – it is not created nor destroyed, it can only be transferred from one object to another.

Whenever there exists a difference in electric potential between two bodies…

Electric charge will flow from the higher electric potential to the lower potential region.

Flow of charge will occur when…

The two bodies are connected by an electrical conductor such as copper wire

Electric current or Current

The flow of charges measured in amperes

Electric Current

Amount of current that flows through an electrical element.

Voltage

The amount of work required to move charge between two points

Electromotive force (emf)

The electric potential difference between an area with an excess of free electrons (negative charge) and an area with electron deficiency (positive charge).

Most common sources of electricity are…

Chemical reaction, light, and magnetism

Direct Current (dc)

Flow of electric charge that occurs in one direction
Typically produced by batteries and direct current
generator

Alternating Current (ac)

Flow of electric charge that periodically reverses
Frequency – the number of cycles per second
Created by generators at power plants

Kirchhoff’s Current Law

At any given time, the sum of currents entering a node must be equal to the sum of the current leaving the node.

Resistance to electrical current depends on…

The material of the wire, its length, diameter, and temperature.

Resistivity

Measures resistance of a piece of material to electric current.

Ohm’s Law

Describes the relationship among voltage, resistance, and current:

American Wire Gage (AWG)

The standard North American system for measuring the diameter of round, solid, and nonferrous electrical wire

Resistors

An electric component that resists the flow of either direct or alternating current

Capacitors

Electrical components that store electrical energy.

Unit for Capacitor

Farad (F)
one farad = 1 coulomb per volt

Primary cell of a battery

A cell that cannot be recharged

Secondary cell of a battery

A cell that can be recharged

Photoemission

The physical process where a material (usually a solid or gas) absorbs incident electromagnetic radiation—such as light, ultraviolet rays, or X-rays—and subsequently emits electrons

Photothermal plants

Solar radiation is used to make steam by heating water flowing through pipes which run through
parabolic solar collectors. Steam is then used in a turbine to drive a generator

Photovoltaic cell

light is converted directly to electricity
 made of gallium arsenide
 approximately 20% conversion efficiency

Electric Motors

Motors drive many devices and equipment that make our lives comfortable and less laborious.

Illumination

Distribution of light on a horizontal surface

Lumens

The amount of light emitted by a lamp

Intensity of illumination

A measure of how light is distributed over an area

Footcandle

A common unit of illumination intensity equal to one lumen distributed over an area of 1-square-foot

Efficacy

The ratio of how much light is produced by a lamp (in lumens) to how much energy is consumed by the lamp (in watts).

Color rendition index (CRI)

A measure of how well a light source renders true colors of an object as compared with direct sunlight

Fluorescent Lights

In a fluorescent tube, electric current is conducted through mercury and inert gases to produce light

High-Intensity Discharge Lamps

produce light by striking an electric arc across tungsten electrodes inside a gas-filled glass tube.

Light Emitting Diode Lights

a semiconductor device that converts electrical energy into light.

Opposite charges repel each other and like charges attract each other.

False

What is the SI unit for electric current?

Amperes

Which quantity represents the amount of work required to move charge between two points?

Voltage

In all batteries, electricity is produced by what?

A chemical reaction.

The flow of electric charge that occurs in one direction that is typically produced by batteries is known as what kind of current?

dc current (direct current)

The flow of electric charge that periodically reverses direction that is typically produced by rotating generators is known as what kind of current?

Alternating Current

Ohm's law describes the relationship between voltage, resistance, and current. What is the formula?

V = I x R

A numbering system that describes the size of an electric conductor is AWG. What does AWG stand for?

American Wire Gage

When it comes to wire size, the larger the gage number, the larger the wire diameter.

False

In certain circuits, if one of the elements fails, that failure prevents the current from flowing through other elements in the circuit; thus, the entire circuit fails. What type of circuit is this?

series circuit

Capacitors are used for…

1) electronic filters

2) energy storage

3) timing elements

A common unit of illumination intensity is called a footcandle and is equal to which of the following?

one lumen distributed over an area of 1 square foot