1. Energy of a magnetic dipole in a magnetic field
You don’t realize it yet, but we have been talking about magnetic dipoles for the last 5 slides.
A current loop, or any other body that experiences a magnetic torque as given above, is called a magnetic dipole.
Energy of a magnetic dipole?
You already know this:
Today:
Electric Dipole
Magnetic Dipole
Homework Hint
Homework Hint

2. Example: a magnetic dipole of moment is in a uniform magnetic field
Example: a magnetic dipole of moment is in a uniform magnetic field . Under what conditions is the dipole’s potential energy zero? Minimum? Under what conditions is the magnitude of the torque on the dipole minimum? Maximum?

3. Example: a magnetic dipole of moment is in a uniform magnetic field
Example: a magnetic dipole of moment is in a uniform magnetic field . Under what conditions is the dipole’s potential energy zero? Minimum? Under what conditions is the magnitude of the torque on the dipole minimum? Maximum? IR  IL  A  B  IL  IR A B
 = 90
Potential energy is zero when
cos  = 0, or when  = 90 or 270.

4. Example: a magnetic dipole of moment is in a uniform magnetic field
Example: a magnetic dipole of moment is in a uniform magnetic field . Under what conditions is the dipole’s potential energy zero? Minimum? Under what conditions is the magnitude of the torque on the dipole minimum? Maximum?  IL  IR A B IR  IL  A  B
 = 0
Potential energy is minimum when cos  = 1, or when  = 0 or 180.

5. Example: a magnetic dipole of moment is in a uniform magnetic field
Example: a magnetic dipole of moment is in a uniform magnetic field . Under what conditions is the dipole’s potential energy zero? Minimum? Under what conditions is the magnitude of the torque on the dipole minimum? Maximum?  IL  IR A B IR  IL  A  B
 = 0
Torque magnitude is minimum when sin  = 0, or when  = 0 or 180.

6. Example: a magnetic dipole of moment is in a uniform magnetic field
Example: a magnetic dipole of moment is in a uniform magnetic field . Under what conditions is the dipole’s potential energy zero? Minimum? Under what conditions is the magnitude of the torque on the dipole minimum? Maximum? IR  IL  A  B  IL  IR A B
 = 90
Torque magnitude is maximum when sin  = 1, or when  = 90 or 270.

7. Example: a magnetic dipole of moment is in a uniform magnetic field
Example: a magnetic dipole of moment is in a uniform magnetic field . Under what conditions is the dipole’s potential energy maximum? IR  IL  A  B
I left this for you to figure out.