1. Effect of Temperature on Resistance
September 20, 2017
Effect of Temperature on Resistance

2. Drill: Take out HW worksheet
Fill in the blanks:
The temperature coefficient of resistivity () represents the change in ___________ in response a change in ____________.
Conductors ___________ resistance in response to an increase in temperature.
Insulators ____________ resistance in response to an increase in temperature.
The equation to solve for a change in resistance due to temperature is __________.
Conductors have a _____________ (positive/negative) temperature coefficient.
Insulators have a _____________ (positive/negative) temperature coefficient.

3. Partner Grade Last Night’s Homework
Switch papers with a partner
Partner: sign the bottom of the paper in pen
Mark the correct answers (3 points per question)
Variables listed = 1 pt
Equation w/variables = 1 pt
Correct Answer w/units = 1 pt
Total the score and write it on the top of the paper

4. Reminders Friday: Mini Quiz (10 points) on Resistance–Temperature
Tuesday: Test on Resistance Unit

5. Resistance Unit Review
September 21, 2017
Resistance Unit Review

6. Drill How many significant figures? 342.7 m 0.0000455 m 0.982 m
3.0 X 103 m m
If you added all of the above measurements, how many significant figures should you have in your answer?
If you multiplied all of the above measurements, how many significant figures should you have in your answer?

7. Whiteboard Review Convert 35.6 mΩ to Ω. Convert 0.056 km to m.
Draw the five graphs we have discussed (length, cross- sectional area, resistivity, temperature-conductor, temperature-insulator)
Explain why a longer wire has higher resistance.
Explain why a thicker wire has lower resistance.
A higher number in ohms = a __________ resistance.

8. Whiteboard Review
Explain why a conductor increases resistance when the temperature increases.
Define resistivity.
Define temperature coefficient of resistivity.
What equation relates resistance, length, cross-sectional area, and resistivity? Specify units.
What equation is used to calculate the change in resistance caused by a change in temperature? Specify units.

9. Whiteboard Review Name two real-life uses of resistors.
A carbon resistor is to be used as a thermometer. On a winter day when the temperature is 4C, the resistance of the carbon resistor is . What is the temperature on a hot summer day when the resistance is ? The temperature coefficient of resistivity is -5 x 10-4/C.
Calculate the resistance of a piece of copper wire that is m long and has a diameter of 1.00 mm. The resistivity of copper is 1.68 x 10-8 m.