Ohm's law lab guidelines

Plan on submitting a draft by Tuesday's class.

Final lab will be due the class after the draft is due.

Lab Questions for "Ohm's Law" lab - please change the title.  If you use "shocking" as part of your title, I'll deduct a point for lazy punning.

So far, you've done 2 graphs: I vs. R, V vs. R. They will be included in the lab. Don't forget titles, units, etc.

Lab questions

1. Examine the 2 graphs. Do they make sense? Why? What's going on in them? Do they appear to obey any mathematical relationship/equation?   Is one graph stranger (or more unexpected) than the other?  Discuss.

2.  Calculate experimental resistances for each pair of V and I - use the equation R = V/I

3. You've just determined experimental resistances for each trial. Are they within 1% (the supposed tolerance) of the expected/theoretical values (the ones on the box)? Should they be? If not, why are they not so good?  Don't forget sources of error, in general.

4. What does it mean exactly if something follows Ohm's Law? Do all electrical devices follow this law? Are there substances that definitely are not "ohm-ic"?

5. Other than the batteries "dying," what might happen as the batteries are connected to the resistors? Would the V and I values change?  Discuss.

6. What is meant by "internal resistance" of the battery, and how does it affect this experiment (your results)?

7. Anything else you want to conclude or talk about.

8.  Hooray!

Lab guidelines (in general) - reposted

Lab Guidelines

The lab writeup should have each of the following items:

Title of Experiment - this is up to you
Your name
Lab partner(s)
Date(s) performed

Purpose - the purpose of the experiment, as it appears to you

Data - in table form, with units.  Give table a title as well.

Graph(s), where relevant - for this harmonic lab, graphs are optional.  They may make your point(s) stronger.

Answers to lab questions - see lab handout

Sources of error and ways to eliminate/reduce error

General conclusion - Talk about what you learned in the experiment.  Analyze data.  Give thoughts and reasoning, where appropriate.  Talk about applications or places where this new knowledge applies.

Make sure it is neat.

LoggerPro download

https://parkscience.pbworks.com/w/page/351271/LoggerPro

password is extrapolate

lab HW

Create 2 graphs (using Logger Pro, or whatever program you like):

Current (I) vs. Resistance (R)
Voltage (V) vs. Resistance (R)

Look at the curves.  Do they make sense?  Start thinking about them.

Also, if you have time:  calculate the experimental resistance values for each trial.  Do this by:

R = V/I

The answers will be your 4th column in your data table.

Hooray!

HW

Please investigate the concept of resistance. Prepare to run a lab comparing voltage, current and resistance (next Monday).

HW

Read about the physics and chemistry of the simple battery.

hw

For next class:

Research L. Galvani's frog experiment.
Find out how this relates to the battery - it may be useful to read about A. Volta.

Enjoy the long weekend!

hw for Monday

1.  Recall the electric field concept.  Draw the field that you would see under these circumstances.  The first two were shown in class:

a.  a positive hunk of charge by itself

b.  a negative hunk of charge by itself

c.  2 hunks of charge close to each other; both are negative

d.  2 hunks of charge close to each other; both are positive

e.  a hunk of positive charge close to a hunk of negative charge

If you want to know quickly if your answers a close to correct, do a google image search for "electric field".  The first few images that show up will have these among them.

2.  Review for quiz:

a.  Calculate the force between 2 charges (5E-6 C, -15E-6 C), when separated by a distance of 0.004 m.

b.  If the distance between these 2 charges were changed to 5 time the original amount, how would the force be different?  Do this without a formal calculation.

c.  Consider the 5E-6 coulomb charge.  How many protons is this?  Recall that 1 proton has a charge of 1.6E-19 C.

d.  What does it mean to be a fundamental particle?  

hw for Thursday

1.  Revisit Coulomb's law - make sure you understand it, and what "inverse square" law means.

2.  Work this problem: Two charges (4 x 10^-9 C, and 9 x 10^-9 C) are separated by a distance of 0.01 m.

a.  What is the force between these charges?
b.  Is this force attractive or repulsive?  Why?
c.  Without exactly calculating it, what would happen to the force if the distance between the charges was tripled?
d.  What would happen to the force if the distance was cut to half the original value?  Try to determine this without calculating.

3.  How many electrons are in -1 C of charge?  How about in -6 C?

4.  Look up electric fields and try to understand:  what they are, and how to draw them.

Let's have a quiz next Wednesday on everything up to and including this Thursday's class.