Thursday, November 25, 2004

Lesson 20

ELECTRICITY LESSON 20 – Measuring Electrical Energy
Lesson: 20.
Take up Hwk: Measuring Electrical Energy Worksheet, other worksheet (series and parallel resistance), Handout, take up cp p.g 80-81
Overhead Watts and Joues – Measuring Electrical Energy
SW/HW: p. 83, 84, 85 (group work post answers on the board to discuss)
Hwk: Try CP pg. 86


Power - follow this link (there are pretty lights and fun cartoons!) http://www.saskschools.ca/curr_content/science9/electricity/lesson05t.html

Electrical energy - follow this link (it's got a much better description than I gave in class)
http://www.need.org/needpdf/infobook_activities/SecInfo/Elec3S.pdf
scroll down the page until you get to the part on electric power and electric energy and how the two are related...
Don't worry if you did not finish all of the assigned course pack information. We will do some of it in class tomorrow!

Wednesday, November 24, 2004

Lesson 19

ELECTRICITY LESSON 19 – OHM’s Law
Lesson: 19.
Take up Hwk: Pg. 319 #1-7, collect labs pg. 75-77, take up pg. 78-79
Quiz
Measuring Electrical Energy Worksheet/Handout
More resistance questions handout
Hwk: Complete Worksheets and course pack lab pg. 80, and pg. 81.


Resistance

1. Resistance is the property of a component which restricts the flow of electric current.

2. Energy is used up as the voltage across the component drives the current through it and this energy appears as heat in the component.
3. Resistance is measured in ohms, the symbol for ohm is an omega . 1 is quite small for electronics so resistances are often given in k and M. 1 k = 1000 1 M = 1000000 .
4. Resistors used in electronics can have resistances as low as 0.1 or as high as 10 M.

Resistors connected in Series

When resistors are connected in series their combined resistance is equal to the individual resistances added together. For example if resistors R1 and R2 are connected in series their combined resistance, R, is given by:

Combined resistance in series: R = R1 + R2

This can be extended for more resistors: R = R1 + R2 + R3 + R4 + ...

Note that the combined resistance in series will always be greater than any of the individual resistances.

Resistors connected in Parallel

When resistors are connected in parallel their combined resistance is less than any of the individual resistances. There is a special equation for the combined resistance of two resistors R1 and R2:

1 = 1 + 1 + 1
__ __ __ __
Rt R1 R2 R3 ...


Monday, November 22, 2004

Lesson 18

OHM's Law

Here's an opportunity to get you doing a little self teaching using the net:

Here is a couple of websites to help you on your way.

The first website teaches you how to perform calculations and gives you a definition of OHM's law:
http://www.grc.nasa.gov/WWW/K-12/Sample_Projects/Ohms_Law/ohmslaw.html

This next site gives you a number of practice questions to get you comfortable with calculating resistance:
http://www.the12volt.com/ohm/page2.asp (make sure that you click the = sign if you want to check your answer)
Hwk:
QUIZ IS POSPONED UNTIL TUESDAY

ANNUAL LEARNING PLANS TO BE COLLECTED ON TUESDAY
VOLTAGE QUESTIONS TO BE HANDED IN TOMORROW CP PG 72 – 74
TODAY’S WORK:
- READ PG 316-319
- COPY DOWN EXAMPLE “SAMPLE PROBLEM” PG. 318
- IN PARTNERS ANSWER QUESTIONS 1-7 – HAND IN FOR COMPLETION
- FINISH ANY UNFINISHED LAB WORK TO BE HANDED IN TOMORROW.
- IF FINISHED EARLY COMPLETE LAB PG 80 IN COURSE PACK.
- STUDY FOR TOMORROW’S QUIZ