Teach Fzx Tuesday - Practical Quiz Failure

A few years ago I started quizzing students on their ability to use an ammeter and a voltmeter by setting up a circuit and requesting that they measure and record the voltage and current between given points in a circuit.  I knew that some of them had been depending on their lab partners to measure everything so I warned them early and often before I gave them the quiz.

Video instructions on using meters

The vast majority of students showed themselves capable of properly using the meters.  Only about 1 or 2 per class had no idea.  Success!

Now I quiz on the proper use of a protractor, a mass balance, and a scale.  This is the first year for the scale and I wanted them to measure the weight of an object supplied.  There were four stations and I directed them to one of the stations during a test on static equilibrium.  

Epic Failure!  Even though I had produced a video for them to use

Video instructions on using a scale

and that video is less than 2 minutes long they didn't zero the scales!  And that was after two class activities and an important lab during which they had to zero the scales.  I emphasized it verbally and demonstrated how to do it in class before each activity and lab.

But they didn't do it even with review questions that read:

• can you properly zero a balance?
• can you correctly measure mass using a balance?
• can you properly zero a scale?
• can you correctly measure weight using a scale?

Only about 25% of HONORS PHYSICS students properly zeroed the intentionally unzeroed scales before measuring weight.

I definitely have to include more of this kind of practical quiz - this one was a revelation.

(BTW - some call it calibration, but it's really not.  Calibration is when we make sure that values on our instruments are the same as the true values.  This zero-ing process is just making sure that the indicator reads zero if there is zero force.)