EM 03a -

SAFARI GUIDE: None Today (Boone, you're moved to tomorrow)

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OPENING QUESTION: Please see Tasque #1 below

SUB: Please allow UP TO 15 minutes only for the following exercise. Students will finish whatever is left AT HOME THIS EVENING! (Honest, they will, really, truly!)

GRACIOUS & HUMBLE STUDENTS:

Tasque #1 (No more than 15 minutes Please)

See how much of the following you can fill in with formulae and/or annotations (feel free to change the order/rearrange as needed). Again, 15 minutes max!

1) There is a force pushing up on the magnet (There MUST be, we can see that by inspection)

2) That force is a magnetic force (It MUST be, there is no other source for the opposing force).

3) The magnetic force MUST be directed upward to impede the motion of the magnet as observed

4) Current/charged particle motion MUST be normal (perpendicular) to the magnetic field and the magnetic force BOTH. We know the direction of the magnetic force-- that means there are only two possible orientations available for the current to move)

5) Magnetic forces are caused by charged particles moving through a magnetic field. Therefore....

6) Changing magnetic fields cause changing magnetic flux

7) Changing magnetic flux causes EMF

8) Emf causes charged particles to move from higher to lower potential

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Tasque #2

EM/Mechanics practice:

Materials required (but please don't start the actual measurement until step #4 below)

1) A scale for measuring the mass of the magnet (I didn't grab a scale before I left yesterday, but I've asked a colleague to grab one from the science stock room). If that didn't happen, please inquire with Ms Berkey across the hall or any other science teacher)

2) A ruler for measuring... something or other (they are found on the side counter)

3) A timer for measuring some sorta event... and yes, you can use your forbidden electronic device as a stop watch.

SUB: Please threaten students with chili/lime grasshoppers (see container on desk) if they use their phones for anything other than timing (they *Do* know better)!

MOST GRACIOUS and HUMBLE students:

Here is a great hands on Free Response practice problem (Oh and please refrain from making ANY actual measurements until you've finished deriving the appropriate formulae!)

1) Beginning with Newton's 2nd Law, please derive an equation that shows the relationship between magnetic force and gravity

2) Please determine an equation that shows the time it will take for the magnet to accelerate down the entire length of the tube

3) Now please derive an equation that shows how you will calculate the actual magnetic force in terms of measurable quantities and known constants/values.

4) Please now commence your measurements and use the equation you derived in #3 above to determine the value of the magnetic force resisting the force of gravity.

Finally, please work with your group and design additional steps to this investigation to determine the maximum current induced in the pipe (hint: you'll probably want to visit the vernier website and see what sorta probes they have that might be helpful)

SUB: I have provided you with hints. Make sure students spend at least 15 minutes working on deriving the equations they need before you allow hints.

Also, if students want/need a hint, it will cost them consumption of one (count 'em 1) chili lime grasshopper (see container on desk).

Grasshopper must be fully consumed by one person in the group.

Water is NOT allowed for a minimum of 2 minutes and 55 seconds thereafter (because I said so!).

No barfing, spewing, yakking, technicolor yawning, buicks, ralphing or any other sort of upchucking is allowed.

SUB: Please post hint on the board for ALL groups to see but ONLY after the successful consumption of said grasshopper (above). That way we'll have one hint for everyone per grasshopper.

Have fun and I'll see you tomorrow (I hope!)