Mid year review

Format

• Part 1:– Multiple Choice : • 33 questions (4 points each)

• Part 2:– Short Answer:• 15 questions (4 points each)

Topics

• Earth and Space– Lithosphere:• Ore vs. Mineral (1)

Lithosphere

Minerals vs. Ore

Mineral Ore

- $ $

Environmental Effects of mining

• Deforestation• Destruction of habitat

• Pollution• Heavy Machinery

Topics

• Material World:– Chemical Changes• Oxidation (1)• Combustion (4)

– Electricity• Charges (4)• Static Electricity (2)• Electricity formulas (9)• Circuit Design (5)

Changes

Changes (5)

• Combustion– Visible signs of rapid combustion– Fire triangle

• Oxidation– Identify an Oxidation reaction

Types of chemical changes

• Oxidation:– Definition:• Chemical change that occurs when a substance reacts

with oxygen (O2)

– Examples• Rusting• An apple turning brown

– Particle Model

Types of chemical changes

• Combustion:– Type of oxidation reaction that releases a large

amount of energy (light and heat)

– Examples• Fire

– Fire Triangle

• Combustion Triangle

Electricity

Elementary particles

• Protons Positive

• Electrons Negative

• Neutrons Neutral

What does this mean…

• An element with more electrons than protons will be considered negatively charged

• A substance with less electrons than protons will be considered positively charged

How do charges react?

• Opposites attract, Like charges repel

Practice Questions

A B B C C D

Practice Questions

If I say that by rubbing silk and glass together, the silk gains electrons.

Will silk be positively or negatively charged?

Static electricity

• 1. Friction

• 2. Conduction

• 3. Induction

Dynamic electricity

• What conducts electricity?– Metals– Graphite– Electrolytes (salts in water)

• Conductivity of a wire– A wire’s conductivity (how much electricity can

pass through in a given time) will

• Increase if the diameter of the wire increases• Increases if the length of the wire decreases• Increases if the temperature decreases• Change with substance used (copper is the best)

Which of the following

copper

copper

10 cm

10 cm A)

B)

25°C

100°C nichrome

10 cm

100°C

copper 10 cm

25°C C)

D)

plastic

Circuits

Circuits (5)

• Electrical functions• Series vs. parallel circuits • Draw a circuit• Connection of an ammeter and voltmeter• Identify the circuit based on description

Circuitry basics• All circuits must have elements that perform the

following electrical functions

– Power supply: Battery– Conductors: Wires– Transform energy: Resistors, Lights

• To that you can add– Control Switch– Protection Fuse

Circuitry Basics

Parallel– More than 1 pathway

– Independent

– Lights controlled separately

– More energy efficient

Series– Only 1 pathway

– Dependant: 1 goes out they all do

– 1 switch controls everything

– Less energy efficient

Drawing a circuit

• Read the question carefully– Find out whether they are asking for a series or

parallel circuit• Draw the circuit (1, 2 or 3 boxes)• Add the power supply• Add and label the necessary components

Adding Ammeter and Voltmeter• An Ammeter– Measures current intensity – Placed directly in the circuit

• A voltmeter– Measures potential difference– Measures 2 points

Questions on Circuits

• A circuit consists of two light bulbs (L1 and L2), a switch, and a power supply. When switch 1 is open L1 stays on and L2 goes out. Close the switch and both lights are on.

• Draw the circuit

VA)

VB)

C)

D)

V

V

A

R1 R 2 R1 R2

A

R1 R2

A

R1 R2

A

A)

B)

C)

D)

What are the electrical functions found in the following circuit?

Formulas

Formulas (9)• Basic Applications– V=RI– E=Pt– P=VI– Qualitative V=RI

• Dual Equations

• Find the most energy efficient appliance (calculate E)

To solve• Read the question carefully

• Underline the important information and highlight what is being asked of you (what should your final answer be)

• Find the formula that has your missing variable in it.

• Identify the remaining relevant information in your question. (If you are missing a second variable you need a second formula)

• Solve the problem

• Do not forget to include your units

• Calculate the resistance value for each of the following resistors

• Resistor– A 2 V 10 A– B 5 V 3A– C 3 V 20A– D 6 V 2A

Question– While having breakfast, you notice the following

information on the specification plate of the toaster.

– You also note that this toaster toasts the bread in 1.5 minutes. What quantity of electrical energy is consumed by the toaster's element to toast the bread?

120 V6 A

60 Hz

Topics• Technological World

– Motion transmission and transformation systems (1)– Speed change and torque (3)– Adhesion and friction (1)– Drawing in Multiview (1)– Drawing developments (1)– Tolerances (2)– Electrical functions (5)– Controls (1)– Resistance coding (3)– Constraints and Properties (2)– How something works (2)

Motion System

Transmission and transformation

Motion Systems

Motion Transmission• Same type of motion

• Gear Train• Chain and Sprocket• Worm and Worm gear• Friction gear• Belt and pulley

Motion Transformation• Different types of motion

• Rack and Pinion• Cam and Follower• Screw gear systems• Slider and Crank

Speed Change

• Speed ratio: driver gear driven gear

Adhesion and Friction

• Adhesion:– when two objects want to stick together– Better adhesion when:• Objects have rough surfaces• Objects are warmer• No lubricants

• Friction: force that opposes motion

TECHNICAL DRAWINGS

Different Views

Multiview• A set of 2D drawings• Uses normal graph paper• Uses all types of lines

Isometric• A single 3D drawing• Uses weird dotted paper• Uses only visible lines

Developments

Tolerance

Tolerance Dimensioning

• Tolerance is the total amount that a specific dimension is permitted to vary;

• It is the difference between the maximum and the minimum limits for the dimension.

• For Example a dimension given as 1.625 ± .002 means that the manufactured part may be 1.627” or 1.623”, or anywhere between these limit dimensions.

Allowance & Clearance

Interchangeable Fit

Electronics

Electrical Functions

• 1. Power supply: – Supplies energy to the circuit– Examples: Battery, power supply, photovoltaic cell

• 2. Conduction:– Ability to transfer electrons

Factors that affect conduction

• Length:– The shorter the wire the better the conductor

• Diameter– The wider the wire the better the conductor

• Temperature– The colder the wire the better the conductor

• Nature of the material– A metal is better than a metalloid (carbon) which is

better than a non-metal

• 3. Protection:– Element whose goal is to protect the circuit in

case of a surcharge

Electrical functions continued

• 4. Insulation: – Element whose function is to slow down the

electrical current

p.468

Electrical Functions

• 5. Control– Component that has the ability to control the flow

of electricity in a circuit

– Flip flop switch, lever switch, push button, magnetic switch

Defining switches

• UniPolar vs. Bipolar • Unidirectional vs Bidirectional

Electrical Functions

• 6. Transformation of energy– Any component that has the ability to transform

electrical energy into another form of energy (heat, light, magnetism, vibration)

• 7. Relay– Function: Element that uses a small amount of

power to switch another circuit which requires a larger amount of power

• 8. Condenser (Capacitor)– Function: Stores energy• Allows to even out current fluctuations• Allows to discharge stored energy in one shot (e.g.

camera flash)

• 9. Diode– Allows the current to flow in only one direction• Has low resistance one way, incredibly high resistance

the other)• Converts Alernating current into direct current

• 10. Transistor– Function: Amplifies an electronic signal– Used in computers – binary code

Materials

Properties

• Hardness• Resilience• Malleability• Ductility• Stiffness• Conductor of heat• Conductor of electricity• Resists corrosion

Properties

• Hardness• Resilience• Malleability• Ductility• Stiffness• Conductor of heat• Conductor of electricity• Resists corrosion

Wood

Properties

• Hardness• Resilience• Malleability• Ductility• Stiffness• Conductor of heat• Conductor of electricity• Resists corrosion

Ceramic

Properties

• Hardness• Resilience• Malleability• Ductility• Stiffness• Conductor of heat• Conductor of electricity• Resists corrosion

Metal