1. Introduction to Electromagnetism
Harsha Wasalathanthri
What's Electromagnetism?

2. On a slightly bigger scale ...

3. Start with magnetic field from a current carrying wire
Right hand rule

4. Calculating force from electromagnet
Start with Ampere's law.
∲B.dl = μIenc ; μ - Permeability of space
B - Magnetic field Ienc- current enclosed by loop
2πRB = μI
B = μI/(2πR) R I

5. Magnetic field from N coils.
Interested in field close to coils, not center of coils.
2πRB = μ(NI)
B = μNI/(2πR)

6. Force on a current carrying wire in a magnetic field
F = BIL

7. Coil on top of “perfect” conductor
Conductor creates magnetic field to cancel external magnetic field
Magnetic field from coil
Magnetic field from conductor

8. Force on coil Force acts symmetrically on coil
Force on a segment of one turn of coil
F1turn = BIL; L = 2πR
= μNI/(2πδ)*I*2πR
= μRNI2R/δ
Ftotal= F1turn *N
=μRN2I2R/δ f f I B δ B
B = μNI/(2πδ)