Ke Arah W. Lab 2 - Resistance Ohms Law DPG PDF

Preview

Summary

lab worksheet, resistance Ohms law
spring 2021...

Description

PHYS 1311L Resistance and Ohms Law Investigation Objectives: 1. Discover what parameters affects the resistance, R, in a circuit 2. Investigate Ohm’s Law and discover what conditions maximize current flow. I. Resistance Sim 1. Goto http://phet-web.colorado.edu 2. Click Simulations, Electricity, magnets, and circuits 3. Select Resistance in a Wire 1. Manipulate each button separately and in your own words what does each variable represent(look at what changes) -

As you decrease the slider for resistivity, p, the resistance decreases and there are fewer specks in the wire. As you decrease the length of the wire the resistance decrease as well and as you increase the area of the wire the resistance also decrease

2. In this sim, what variables are you seeing the relationship of. Write the formula below, and indicate the units used to measure each one. ρL A

R=

→

=

( Q∗m) m cm2

3. Try increasing the resistivity of the resistor, . How does this change the “look” of the resistor? Describe how that relates to the formula you just wrote (direct, indirect relationships, etc.). What happens to the value of “R” (Resistance)? Is this something that can be changed in a resistor that you would buy in a store to use in a circuit? -

If you increase the resistivity the wire has more black dots in it. The values og R increases as the value of ρ increases. Yes, different types of wires have different resistivity. Example: the resistivity of aluminum is less than wood so if you buy a circuit made of aluminum it will have less resistance than one made of wood

4. Now increase the length (L) (you would essentially be designing a different resistor, since you can’t do this to one you will be using in a circuit). What happens to “R”? WHY? -

As the length of the wire increases, the resistance increases because the wire has a longer distance to conduct the electricity

5. Now increase the area (A) of the resistor. What changes? WHY? -

The value of R decreases because there is more space for the electricity to travel

6. Write a summary about the different relationships you looked at in the properties and measurements of a resistor. - the length, area, and resistivity of a wire directly affect the resistance of it

II. Ohms Law Sim 1. Close the Resistance in a Wire Sim 2. Open the Ohm’s Law Sim 1. Manipulate each button separately and in your own words what does each variable represent(look at what changes) -

As the voltage is increased the voltage increases, and as resistance increases the current decreases

2. Manipulate the buttons. What conditions maximize current? -

A very high voltage and low resistance

3. What conditions minimize current? -

A very voltage and high resistance

4. What would happen if you could decrease the resistance to 0? Explain. -

There would be a infinite current because current equals voltage divided by zero resistance

5. Move the potential (volts) and resistance (ohms) sliders and observe the current (amps) a. As voltage increases, current __increases__. b. As resistance increases, current _decreases_. c. Fill out the table below and check your work in the simulation  Remember, the simulation shows milliamps.  You should show Amperes in the table V I R 8.0 V 0.01 A 800 Ω 2.0 V

.044 A

45.45Ω

2.5 V

.0058 A

430 Ω

6.9 V

.069 A

100 Ω

6.4 V

0.0213 A

300 Ω...