Energy and Power Fundamentals Ch8 – Pt1

What is Energy?  We use energy every day Bodies Vehicles Machines Heating/cooling Light

Energy and Work  Energy is the capacity to do work or to make an effort.  Work is using force to act on an object in order to move that object in the same direction as the force.

Types of Energy  Potential energy is stored energy, or energy at rest.  Kinetic energy is energy in motion.  Technology takes forms of potential energy such as oil, natural gas, and water stored behind a dam, and turns them into kinetic energy. Whenever we use energy it is kinetic energy.

Forms of Energy  All energy can be classified into six basic forms: Mechanical Thermal Radiant Chemical Electrical Nuclear  Each form can be changed into all other forms

Mechanical Energy  Mechanical Energy is the energy of motion Usually visible Every moving object

Thermal Energy  Thermal Energy is heat Heat is given off by movement of the atoms and molecules in a substance The faster they move the more heat energy produced

Radiant (Light) Energy  Radiant (Light) Energy radiates outward in all directions. Occurs as photons (tiny particles within atoms) escape into the surroundings

Chemical Energy  Chemical Energy is released when the bonds between atoms in molecules are broken and the atoms rearranged.

Electrical Energy  Electrical Energy is the flow of free electrons (tiny particles within atoms) from molecule to molecule within conductors.

Nuclear Energy  Nuclear Energy is contained within the nucleus of atoms. It is released when atoms of certain substances, such as uranium, are split apart in a nuclear reaction.

Energy Efficiency  Efficiency is the ability to achieve a desired result with as little wasted energy and effort as possible.  When technology systems use energy, some is always wasted. However, some systems are more efficient than others.

What is Power  Power is the measure of work done over a certain period of time as energy is converted from one form to another or transferred from one place to another.  Power helps us measure how fast the work is accomplished.  Power is commonly measured in horsepower (hp) This measurement is based on the amount of work a horse can accomplish in a certain period of time.

Forms of Power  Three forms of power are commonly used in technology: Mechanical Electrical Fluid Power

Mechanical Power  Mechanical Power is a measure of the work done by means of mechanical energy over a certain period.

Electrical Power  Electrical Power is a measure of the work done by electrical energy over a period of time.

Fluid Power  Fluid Power is produced by outside energy sources, such as a motor. The fluids transmit the energy Fluids themselves are not the source of fluid power  Pneumatic power is a measure of work produced using pressurized gases.  Hydraulic power is a measure of the work produced by putting liquids under pressure.

Energy and Power Systems  Energy and power systems require the same seven resources as inputs People Information Materials Tools and machines Energy Capital Time

Like all technology systems, energy and power systems have inputs, processes, outputs, and feedback

Controlling Energy and Power  Energy and power are used by all technology systems.  In order to use energy effectively, we must control it.

 Before building a system to control energy and power, technologists must consider three main questions What is the original source of the energy? How will it be changed and/or moved from one place to another? How will it eventually be used?  Other factors that must be considered include where the energy source is located, the amount of energy that must be produces, and the length of time it must be controlled.

Storing Energy  Energy can be stored only as potential energy.  The most common way of storing potential energy is in batteries.

Transporting Energy  Potential energy is often easy to transport, such as in the forms of fuels. gasoline  We can also transport kinetic energy Electricity  Mechanical energy can also be transferred over short distances by means of belts, gears, and shafts.  Pneumatic and hydraulic systems can be used to transmit energy as well.

Impacts and Effects of Energy and Power Technology  Environmental Impacts  Depletion of Resources

Quick Review  Q – What is energy?  A - Energy is the capacity to do work or to make an effort.  Q – What is work?  A – Work is using force to act on an object in order to move that object in the same direction as the force.

 Q – There are 2 forms of energy, what are they? What is the difference? Give an example for each.  A - Potential energy is stored energy, or energy at rest. Kinetic energy is energy in motion.

 Q – What are the 6 forms of energy?  A – Mechanical Thermal Radiant Chemical Electrical Nuclear

Activity  Kinetic and Potential Energy Exploration

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Energy and Power Fundamentals Ch8 – Pt2

Measuring Energy and Power  Work, power, force, torque, pressure, heat

Measuring Work  Work is using a force to move an object.  Measured in foot-pounds (ft.-lbs.)  Work = weight (pounds) x distance (feet)

 How much work does a 150 pound man accomplish by climbing a 25 foot flight of stairs? Work = weight x distance Work = 150lbs x 25ft Work = 3,750 ft-lbs

Measuring Power  Power is a measure of the work done over a certain period of time.  Measured in horsepower (hp)  One horsepower is equal to the energy needed to lift 550 foot- pounds in 1 second  Hp = weight (lbs) x distance (ft) seconds x 550

 How many horsepower would the 150 pound man climbing a 25 foot stairway develop over 15 seconds? hp = weight (lbs) x distance (ft) seconds x 550 hp = 150lbs x 25ft 15seconds x 550 hp = 3750 ft-lbs 8250 seconds hp = 0.45

Measuring Force  Force is any push or pull on an object.  Force can be used instead of weight to calculate the amount of work done  Work = force x distance

 Suppose a man pushes a 200 pound barrel of nails a distance of 10 feet along a floor. He uses 55 pounds of force. How much work does he accomplish? Work = force x distance Work = 55 lbs x 10 ft Work = 550 ft-lbs

 Force can also be used instead of weight to calculate horsepower.  hp = force x distance seconds x 550

 How much horsepower does the man produce if it takes him 15 seconds to slide the barrel along the floor? hp = force x distance seconds x 550 hp = 55 lbs x 10 ft 15 seconds x 550 hp = 550 foot-lbs 8250 seconds hp = 0.067

 In the metric system, force is measured in newtons (N) instead of pounds  Two other types of force used in measuring energy and power are torque and pressure.

Measuring Torque  Torque is a turning or twisting force  Torque is applied with a circular motion, and measuring it involves using the radius (distance from the center) of the circle.  Torque is calculated in pound-feet by multiplying the force used by the radius of the object being turned.  Torque = force (lbs) x radius (ft)

 Suppose a mechanic uses 30 lbs of force to turn a wheel that has a radius of 1.5 ft. What is the torque? Torque = force (lbs) x radius (ft) Torque = 30 lbs x 1.5 ft Torque = 45 lb-ft

Measuring Pressure  Pressure is force spread out over a certain area. The area is measured in square inches and its size (length x width) must be calculated first.  Pounds per square inch  pressure = force ÷ area

 Suppose you want to store a 60 pound weight on a shelf. Its base measures 10 inches by 8 inches. How much pressure does it exert on the shelf? Area = length x width Area = 10 in x 8 in Area = 80 sq in Pressure = force ÷ area Pressure = 60 lbs ÷ 80 sq in Pressure = 0.75 lb per sq in

 In the metric system pressure is measured in pascals, or the force of one newton acting on an area of one square meter.

 Units of pressure are commonly used to measure the force of liquids and gases, as in the pneumatic and hydraulic systems.  Force = pressure x area

 Suppose you want to calculate the force of the air compressed inside a balloon. The air pressure is ¼ psi and the inside surface area of the balloon is 80 square inches. Force = pressure x area Force = ¼ psi x 80 sq in Force = 20 lbs

Measuring Electricity  The basic unit for electricity is the coulomb One coulomb is enough to light an average lightbulb for one second  Other measures are made of amperage, voltage, resistance, and wattage.

 Amperage (I) is the rate at which current flows through a conductor. The single unit is the ampere.  Voltage (E) is the pressure that pushes current through a conductor. The single unit is the volt.  Resistance (R) is the opposition to the flow of current. A single unit is the ohm.

 Ohm’s law is a mathematical formula using amps, volts, and ohms. It states that it takes one volt to force one amp of current through a resistance of one ohm.  voltage (E) = amperage (I) x resistance (R)  If you have any two of the measurements you can calculate the third.

E = I RI = E R = E R I E IR

 IF a circuit has a resistance of 20 ohms and a voltage of 120 volts, what is the amperage? I = E ÷ R I = 120 ÷ 20 I = 6 amperes

 Electrical power is measured in watts. Watts are calculated by multiplying amps times volts  P = I x E

 If a hair dryer produces 1,000 watts of power and the voltage is 120, how many amps flow through it?  I = P ÷ E  I = 1,000 watts ÷ 120 volts  I = 8.3 amps

Measuring Heat  Heat energy is measured in Btu’s (British thermal units). One Btu is the heat needed to raise the temperature of one pound of water one degree.  Heat energy is often measured in Btu’s per hour.  Heat energy can be changed into power with engines, but is not an efficient process.

Quick Review  Q – What is the formula for work?  A - Work = weight (pounds) x distance (feet)  Q – What is force?  A - Force is any push or pull on an object.

 Q – What is Ohm’s Law?  A – Ohm’s law is a mathematical formula using amps, volts, and ohms.  Q – What is current measured in?  A – Amperes  Q – What is voltage measured in?  A – Volts  Q – What is resistance measured in?  A - ohms

 Q – Draw the Ohm’s law circle and use it to derive the formulas for Voltage, Current, and Resistance.  A - E I R E = I RI = E R = E R I

Activity  Rubber Band Powered Vehicle  Day 1 – Research and Development  Day 2 – Building and Testing  Day 3 – Competition and Reflection