No resistance
One of my 1st year classes has just been doing the "EMF and r" lab. Before I could run this lab I had to repair all of my multimeters that due to abuse by former students all had blown fuses. If the fuses are to be blown again then it will happen in this lab. Students are given a huge pile of resistors and have to measure the current flowing from a 9V battery. To prevent damage to the meters, before they started, I told the students to calculate the value of R that would cause a current of 0.2A to flow. This seemed to work as no one blew a fuse. Maybe I should simply remove the low values. Never thought of that. Whilst on the subject of low resistance, some students were interested by the resistors with 0Ω. They even have the tolerance quoted as 1% which makes the absolute uncertainty zero! Very cheap superconductors? Actually not, they are simply included to be used as connecting wires in circuit boards with standard slots for resistors ( I didn't know that but one of the students googled zero resistance or something). The lab went quite well I think although the draw that used to contain a set of well ordered nicely label resistors now contains a big pile of mixed up resistors. I hope the students doing the lab tomorrow aren't colour blind.