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

2. 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”

3. Michael Faraday ( )
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

4. 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)

5. 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

6. “Lab” 1 DC motors You need: AA battery Slightly larger magnet
Copper wire
Nail to make dent
in battery terminal