Phy2005 Applied Physics II Spring 2017 Announcements: Monday: discussion of midterm course corrections Today: DC motor activity, practice with magnetic field problems

Reminder: torque on a loop DC motor: current loop in fixed magnetic field X X X X Switched I-direction here! “brushes”: electrical contact with moving commutator “commutator ring”

Michael Faraday (1791-1867) Faraday asked: Can we use magnetism to produce electricity? (next week!) Before we get to that Let’s look at some of his other experiments Michael Faraday

Faraday’s unusual background made it unlikely that he would ever learn science Poor – apprenticed in the bookbinding trade Sandemanian Very little education – no mathematics A couple of factors came together to make the unlikely happen Very intelligent mind Very industrious Lucky break: hired by Sir Humphrey Davy (Royal Institution) when Davy was blinded by lab accident (1812)

Very soon after he learned about Oersted’s experiment Faraday did one of his own He showed how to use electromagnetism to produce mechanical force He invented the electric motor Faraday motor video

“Lab” 1 DC motors You need: AA battery Slightly larger magnet Copper wire Nail to make dent in battery terminal https://www.youtube.com/watch?v=VhaYLnjkf1E