1. Unit 4 Day 3 – Magnetic Dipole Moment & Applications
Magnetic Torque
Magnetic Dipole Moment
Potential Energy of a Magnetic Dipole
Magnetic Moment of a Hydrogen Atom
Applications of magnetic Dipole Moment

2. Magnetic Torque
When a loop of wire carrying a current is placed in a uniform magnetic field, the magnetic force will produce a torque on the loop, causing it to rotate
This is the principle behind motors, analog voltmeters, and etc.

3. Magnetic Torque The torque on the dipole is:
If the coil consists of N loops the current increases by N·I

4. Magnetic Torque
If the coil makes an angle θ with the magnetic field, the magnetic force remains the same but the lever arm is reduced from ½b to ½bsinθ
Torque is always in the direction of the net force
Although this formula was derived for a rectangular coil, it is valid for any shape of flat coil

5. Magnetic Dipole Moment
The quantity NIA in the torque formula is called the “magnetic dipole moment”
Where the direction of A is in the direction of μ
Therefore, in vector form, torque is expressed as:

6. Magnetic Dipole Potential Energy
Remember the torque on an electric dipole:
The electric potential energy of the electric dipole is:
Hence, the magnetic potential energy of a magnetic dipole is:

7. Magnetic Moment of a Hydrogen Atomvt
The hydrogen atom consists of a (-) charged electron orbiting a (+) charged proton
The Coulombic force of attraction is the equivalent of the centripetal force keeping the electron in orbit FC

8. Applications of Magnetic Dipole Moment
Electric Motors Voltmeter (Galvanometer)
Loud Speaker