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JAMSASC
Sunday, November 2, 2014
Tuesday, September 16, 2014
Thursday, February 20, 2014
Significant Figures
Topic: Significant Figures
Specific Objectives: Students should be able to :
1. State the number of significant figures in a number.
2. Express a number to a given number of significant figures.
Strategies: Discussion, Classwork, Demonstration, Video.
Teaching Aids: Overhead Projector, IBT
Instructional Materials: PowerPoint Presentation, CXC/CSEC Physics Textbook
Presentation: In Physics significant figures are a representation of the precision of a measuring instrument, therefore 2.0 and 2.00 taken as readings from 2 different instruments suggest that 2.00 was taken using an instrument of greater precision.
Development and summary of lesson: The lesson will be in the form of a discussion/lecture. The lesson will begin with the teacher giving a summary of what will be done in class. The teacher will discuss the importance of significant figures in physics. Students will then be shown two videos from Youtube on how to determine significant figures. Two examples will be done to show how we round off numbers to a given number of significant figures. The students will then be asked to give answers to similar examples. The lesson will continue with the teacher going through the different rules governing how the number of significant figures in a number is determined. Several examples of the different cases will be done and the teacher will then give the students some questions to do on their own.
Evaluation of Lesson and assignment given: Questions will be set to test the students understanding of what was done. The students work will be collected and marked and the answers discussed at a later date.
Significant Figures - Rules
Significant figures are critical when reporting scientific data because they give the reader an idea of how well you could actually measure/report your data. Before looking at a few examples, let's summarize the rules for significant figures.
- 1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant.
- 2) ALL zeroes between non-zero numbers are ALWAYS significant.
- 3) ALL zeroes which are SIMULTANEOUSLY to the right of the decimal point AND at the end of the number are ALWAYS significant.
- 4) ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant.
Notes: Significant Figures
JAMSASC
EXCEL BEYOND EXPECTATIONS CXC/CSECPhysical Quantities and Units
Subject: Physics
Topic: Physical Quantities and Units
Specific Objectives: Students should be able to:
1. Recall the fundamental Quantities of the international system and their related symbols.
2. Recall the base units for the fundamental quantities in the SI system and their related symbols.
3. Explain the need for standard units in measurement.
Teaching strategies: Discussion, Classwork, Lecture, video, demonstration.
Instructional Materials: Syllabus, Physics textbook
Lesson Introduction: The SI is a system of units used in physics. There are seven basic quantities having seven basic units and these are used to derive all other quantities.
Development and summary of lesson: The SI system will be discussed and students will be given the different quantities and units that are taken as basic. The symbols used for the quantities and units will also be given in tabular form.
The need for using these standard units will be discussed as well as problems that may arise when using non-standard units.
Evaluation Of lesson: At the end of the lesson, question will be given to the students to test how well they understand the concepts taught.
THE SI SYSTEM
The SI system (International System of Units) is the modern metric system of measurement and the dominant system of international commerce and trade. SI units are gradually replacing Imperial and USCS units.
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Derive Units
Derived units are algebraic combinations of the seven base units and the two supplementary units with some of the combinations being assigned special names and symbols.
JAMSASC
EXCEL BEYOND EXPECTATIONS CXC/CSEC
Fuse and Circuit Breakers
Subject: Physics
Topic: Fuse and Circuit Breakers
Objectives:
1. Discuss The reasons for using parallel connections for domestic appliances
2. Explain the purpose of a fuse or circuit breaker.
3. Select a fuse or circuit breaker of suitable current rating for an appliance.
4. Explain the function of the Earth Wire.
5. Recall the international insulation color code.
6. Stare the adverse effects of fluctuating voltage supplies.
Teaching Strategy: Discussion, Multimedia Presentation, including, Music, Videos.
Content and Facts: A fuse or circuit breaker is a device use to protect circuit components from excess currents.
Wires are color coded for safety.
Introduction:
Lesson Development: The function of the fuse/circuit breaker will be discussed. labelled diagram of a fuse will be shown. Questions will be used to show how a fuse rating is calculated. The function of the fuse earth wire will be discussed. The international insulation color code will be displayed in a table and discussed. The effects of fluctuating voltages will also discussed.
Conclusion: a fuse protects the circuit from excess current. An earth wire prevents shock caused by stray currents.
NOTES
FuseThere are many different types of fuses for residential and commercial use, but the most common type is made up of a metal wire or filament that is enclosed in a glass or ceramic and metal casing. In a home, the fuse is typically plugged into a central fuse box where all the building’s wiring passes through. When the electricity is flowing normally, the fuse permits the power to pass unobstructed across its filament, between circuits. If an overload occurs, the filament melts, stopping the flow of electricity.
Fuse and Circuit Breakers Video
It generally takes very little time for the filament in the type of fuse used in a home to melt, so any power surge is quickly stopped. Once a fuse is blown, however, it must be discarded and replaced with a new one. There are many different voltage ratings available that handle different capacities of electricity, and the best fuse for a circuit is typically one that is rated for slightly higher than the normal operating current.
Circuit Breakers Video
A circuit breaker works in one of two ways, with an electromagnet (or solenoid) or a bi-metal strip. In either case, the basic design is the same: when turned on, the breaker allows electrical current to pass from a bottom to an upper terminal across the solenoid or strip. When the current reaches unsafe levels, the magnetic force of the solenoid becomes so strong that a metal lever within the switch mechanism is thrown, and the current is broken. Alternately, the metal strip bends, throwing the switch and breaking the connection.
Advantages and Disadvantages Of Fuse and Circuit Breakers
The fuse and circuit breaker both have advantages and disadvantages, each of which can depend on the situation in which they are used. Fuses are inexpensive and can be purchased from any hardware store. They also tend to react very quickly to overloading, which means that they can offer more protection to sensitive electronic devices. This quick reaction can be a disadvantage, however, if the circuit is prone to surges that regularly cause fuses to blow.
Fuses must always be replaced once they are blown, which can be challenging in a darkened room or if the appropriate replacement is not immediately available. Another issue is that a do-it-yourselfer can mistakenly select a fuse that has a voltage rating that is too high for his needs, which can result in an overheated circuit. In addition, there may be exposed electrical connections in a fuse box, which can pose a danger to someone who does not follow the proper safety precautions.
Circuit breakers have many advantages, not the least of which is how quickly they can be reset. It is usually clear which switch has tripped, and it can be easily reset in most cases. For the average homeowner, it is also safer because there is no question about choosing the right fuse rating and all of the electrical connections are hidden in a breaker box.
A drawback to using a circuit breaker is that it is usually more expensive to install and repair. A circuit breaker also typically does not react as quickly as a fuse to surges in power, meaning that it is possible that electronics connected to the circuit could be damaged by "let-through" energy. It also is more sensitive to vibration and movement, which can cause a switch to trip for reasons unrelated to an electricity overload.
A fuse and circuit breaker are not interchangeable for all power applications. For example, a fuse cannot be used in situations that require a GFCI. Electricians are best qualified to determine whether a fuse or circuit breaker system is better for a particular electrical installation or upgrade.
The earth Wire
JAMSASC
EXCEL BEYOND EXPECTATIONS CXC/CSEC
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