Download Unit D: Section 2.0


Science 9
Year End Review: Unit D – Electrical Principles and Technologies
Name
Date
Key Concepts
o
o
o
o
o
electric charge and current
circuits
electrical energy storage
energy transmission
measures and units of electrical energy
o
o
o
o
o
electrical resistance and Ohm’s law
forms of energy
energy transformation
generation of electrical energy
renewable and non-renewable resources
THINGS TO STUDY
Section 1.0
Electrical Energy can be Transferred and Stored




Section 2.0
Technologies can be Used to Transfer and Control Electrical Energy





Section 3.0
Different substances provide various levels of resistance to electric current  electricity flows more easily
in conductors than in insulators.
Electrical resistance is measure in ohms, voltage is measured in volts, and current is measured in
amperes.
Ohm’s law states that the current flowing through a conductor is proportional to the voltage applied to it.
Meters are used to measure electricity  voltmeters measure voltage, ammeters measure current,
ohmmeters measure resistance, and multimeters measure all three.
Series circuits provide a single pathway for current, while parallel circuits provide multiple pathways for
current.
Devices and Systems Convert Energy with Varying Efficiencies






Section 4.0
The two types of electricity are static and current  static is electrically charged particles at rest and
current is flowing electrically charged particles.
Voltage is a measure of how much electrical energy each charged particle carries.
Current is the rate at which charged particles flow.
Electricity can be produced through chemical reactions and stored in different types of cells  cells can
be combined to form batteries.
Energy exists in different forms (ex. chemical, thermal, mechanical, and electrical energy).
Energy can be transformed from one form to another  ex. thermocouples change thermal energy into
electrical energy, and electric motors convert electrical energy to mechanical energy.
Power is the rate at which a device converts energy  P = IV
Energy is the ability to do work  E = Pt
Einput and usable Eoutput can be compared to determine the efficiency of an energy-converting device.
Reducing the amount of energy wasted by devices that convert energy increases their efficiencies.
The Use of Electrical Energy Affects Society and the Environment





A variety of alternative energy source can be used to generate electrical energy  ex. fossil fuels,
nuclear energy, geothermal energy, biomass, hydroelectricity, tides, wind power, and solar energy.
Energy sources are either renewable or non-renewable.
Electrical generation can produce by-products and effects that harm the environment.
Energy and non-renewable resources can be conserved through choices that reduce consumption.
Sustainability means using resources at a rate that can be maintained indefinitely.
Unit D: Section 1.0
1. What is the difference between static and current electricity?
2. Explain how an object becomes “charged”.
3. Describe and illustrate the law of electrical charges.
4. What are the four components of a circuit?
5. What is electrical energy?
6. What is voltage? What are the units for voltage? What device measures voltage? What is the
formula for voltage?
7. What is a short circuit? How can you prevent a short circuit from doing harm to people or expensive
electrical equipment?
8. What is the purpose of a lightning rod?
9. What is the difference between a fuse and a circuit breaker?
10. How is electrical energy produced from chemicals?
11. What is the primary difference between a wet cell and a dry cell?
12. What are the components of a cell?
13. What is the difference between a primary and a secondary cell. Give two examples of what devices
would use them.
14. Complete the following table summarizing electrochemical applications.
Application
Description
Example
Electrolysis
Electroplating
Anodizing
Electrorefining
Unit D: Section 2.0
1. Explain the difference between conductors, semi-conductors, and superconductors. How are they
different from insulators?
2. What is resistance? What are the units for resistance? What device measures resistance?
3. What factors affect the resistance in a wire and how does each factor affect resistance?
4. According to Ohm’s law, what is the relation ship between current, voltage, and resistance? Write
the formula for this relationship.
5. In what applications are variable resistors or rheostats used?
6. Describe and illustrate the difference between current and voltage using a model.
7. What is current? What are the units for current? What device measures current? What is the
formula for current?
8. Identify or illustrate the electrical circuit component/symbol in the table.
wire
resistor
cell
variable
resistor
lamp
9. Illustrate a



series circuit and a parallel circuit using the following:
power source = 4 cells
loads = 3 resistors
as many switches as you think you need.
Series Circuit
Parallel Circuit
10. What are transistors used as and in what devices are they commonly found?
Unit D: Section 3.0
1. What is energy? What are the units of energy? What is the formula for energy?
2. What energy transformations occur in the following devices?
a) electric kettle
__________________________________________________________
b) battery-operated car
__________________________________________________________
c) electric blanket
__________________________________________________________
3. Describe how a thermocouple is made. How does it work? What energy transformation occurs when
it is used?
4. Describe how a device, such as a generator, converts mechanical energy into electrical energy.
5. How is an electromagnet constructed?
6. Complete the following table summarizing the components of a motor.
Component
Description
electromagnet
commutator
brushes
armature
7. What is the difference between AC and DC current?
8. What is electromagnetic induction?
9. What is power? What are the units of power? What is the formula for power?
10. Complete the following power problems. Show your work!
a) What is the power of a hair dryer that requires 8 A of current on a 240 V circuit?
b) An 850-W oven requires a 7 A current. What is the voltage?
c) A flashlight uses two 1.5-V batteries to light a bulb that can work on a current up to 0.5 A. What
is the maximum power of the bulb?
9. Add these appliances to each house circuit as directed and calculate what the current is. If the circuit is
overloaded, colour the circuit breaker red.
10. What does the law of conservation of energy state?
11. What is most energy in mechanical devices lost as?
12. How is the efficiency of a device determined mathematically?
Formula:
Explanation:
13. Calculate the efficiency of an 8000-W kettle that takes 6 minutes to boil water. To heat the water to the
boiling point, it takes 200,000 J of energy. Show your work!
Unit D: Section 4.0
1. Briefly describe the process of electrical generation from the burning of coal.
2. Other than fossil fuels, list nine alternative sources of energy.
3. What is the difference between renewable and non-renewable resources?
4. What harmful by-products result from electrical generation and how do they effect the environment?
5. What is meant by sustainability?