A block - review combination circuit

E block

Lab draft due next Wednesday - final lafy due on Friday.  

Attention A block

Draft of lab will be due on Tuesday.

I'd like you to have a little more time to make it great. 

Final lab due next Thursday.

That said, review series and parallel circuits.  Make sure you understand them.

Ok?  Ok!

Lab Guidelines (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.

Series and Parallel - for A block

Folks in A block -

The earlier posting is about the lab stuff.  Here are a couple of review questions related to yesterday's class,

1.  You have 3 resistors:  3, 5 and 12 ohms.  They are in series with a 30-V battery.  Find all currents and voltages in the circuit.

2.  Consider the parallel problem from yesterday:  1, 2 and 3 ohms in parallel.  Now that you know the total resistance (6/11 ohms), find all voltages and currents in the circuit.

Bring circuit and/or lab questions to class Wednesday.

Yay!

lab stuff

A - Draft due Friday

E - Draft due Monday

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!

HW

A-finish graphs (V vs. R, and I vs. R).

Examine the data and see if things make any sense to you.  Consider how and why the V and I change (if they do) and what kind of relationships are at work.

E - investigate the concept of resistance. Prepare to run a lab comparing voltage, current and resistance (next Tuesday).

HW

E block - quiz Wednesday

A block - investigate the concept of electrical resistance

hw

For Tuesday's E block class:

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

Quiz Thursday

For Monday's A block class:

You still have a quiz.  Sorry.  Have a look at the practice problems posted earlier.

pre-quiz practice

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's A block class:

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

Quiz Monday

For Wednesday's E block class:

Apparently, the Electric Field applets (nor any applets) are working on most computers (even if you update your java).  Try to find out how to draw electric fields.  If time allows, do the homework above.

Quiz next Tuesday