1. Good Luck! Exam 2 Review Phys 222 – Supplemental Instruction
Sunday Session As Normal, Informal Q/a

3. The correct solution process is the right answer

4. Do you know all the following?

5. Circuits
Current, Voltage, Resistance, Ohm’s law
Power, Real Batteries, measuring tools (ammeter etc)
Analyze circuit diagrams and circuits with multiple voltage sources
Combining circuit elements, reducing circuits to equivalent setups

6. Magnetic fields
Field lines
Impact on moving charges
Relation to Electric field
Magnetic forces (Lorentz force)
On currents and current loops
Hall effect
Fields Generated by current (Biot-Savart law)
Ampere’s law
Magnetic dipoles, dipole interaction

7. Induction
Faraday’s law
Lenz’s law
Eddy currents
Magnetic materials
Paramagnetism, diamagnetism
Inductors and energy storage
Time varying circuits
LR, LC, LRC
Phasor Diagrams
Resonance Conditions
Transformers

8. Here we go!
Lots of test problems with tips sprinkled in

9. E
SP09

10. RHR
Really all the uses are subsets of just two right hand rules and can be gotten from the two.
1. RHR cross rule.
Point fingers in direction of first vector, curl fingers toward second vector and thumb points in the direction of the resultant.
2. RHR curl rule.
Point thumb in direction of current and fingers curl in direction of B field.

11. Right Hand Rule(s)! Torque on a magnetic dipole
Use standard RHR, cross product
Magnetic Force on a moving charge, by a field
Magnetic Field generated by a current
Thumb in direction of current, fingers curl in direction of field.
Circulation integrals
Curl fingers in direction of integration, thumb points in direction that positive current flows.
Induced current (Faraday’s law)
Thumb in direction opposing change in magnetic flux, fingers curl in direction of the induced current.

12. E
Sp13

13. 𝑀𝑎𝑔𝑛𝑒𝑡𝑖𝑐 𝐹𝑖𝑒𝑙𝑑 Field produced by a charge, moving at speed v:
𝑩= 𝜇 0 4𝜋 𝑞𝒗× 𝒓 𝑟 2
Use RHR to determine direction the magnetic field points (modified curl version)
Field produced by many charges, aka current:
𝒅𝑩= 𝜇 0 4𝜋 𝐼𝒅𝒍× 𝒓 𝑟 2
Once again, dl x r just means to use the modified (curl) RHR
This equation is perhaps easier to use as:
𝑩= 𝜇 0 4𝜋 𝐼𝑳× 𝒓 𝑟 2

14. C
SP13

15. B
SP 09

16. D
SP 09

17. D
Sp13

18. Combining components Parallel Series Resistors / Inductors Capacitors
Addition
T = X1 + X2 +…
Inverse Addition
1/T = 1/X1 + 1/X2 +…
Parallel
Inverse Addition
1/T = 1/X1 + 1/X2 +…
Addition
T = X1 + X2 +…
Series

19. A
Sp09

20. Field lines! Magnetic field lines are loops, no start or end!
Magnetic field lines appear to leave North pole and enter south pole.
Line density indicates field strength

21. A
SP12

22. D
SP 13

23. A
SP 12

24. Faraday’s law 𝑅𝑒𝑔𝑎𝑟𝑑𝑠 𝑐ℎ𝑎𝑛𝑔𝑒𝑠 𝑖𝑛 𝐹𝐿𝑈𝑋
Flux changes are changes in magnetic field strength or area of the loop enclosed.
Remember Magnetic flux is the integral of B•dA
Usually BA
The induced current always opposes the change in magnetic flux.
If flux is decreasing, it will try to increase it, and vice versa
Lentz’s law
Sign’s?
Always check your signs at the end with reality and Lentz’s law. It’s easy to get negative signs messed up in Magnetism.

25. D
SP 13

26. Ampere’s Law: ∫B•dl = µ*Iencl
Solve these problems just like Gauss’s law problems!
Draw a picture.
Pick a good Gaussian surface. Symmetry!
Write expression of integral (if B|| A then, BA)
Write expression for Gauss’s Law involving enclosed magnetic field
Set the expressions equal and eliminate variables to solve.

27. E
SP 12

28. Inductor and Capacitor Behavior
Capacitors:
Initially: Ideal Wire
Long time: Open Switch
Inductors:
Initially: Open Switch
Long time: Ideal Wire

29. A
SP 12

30. Formulas, Formulas The new material has formulas on page 3 mainly.
Don’t forget µo is a constant (on pg 1)
Think about dot products and cross products geometrically.
Dot products give parallel components
Cross products give perpendicular components
Make sure to know the formulas vs the definitions.

31. B
SP 12

32. Hodgepodge
Of relevant questions

33. E
SP14

34. A
F11

35. B
SP 14

36. D
F11

37. A
SP11

38. C
SP14

39. B
F11

40. A
SP 11

41. C

42. Type
Susceptibility
Reaction in Field
Physical Description
Example
Diamagnet
< 0 (small)
Weakly Repelled (normal ‘non-magnetic’ materials)
Weak anti-alignment of material’s dipoles
Wood, Water
Paramagnet
> 0 (small)
Weakly attracted
Weak alignment of dipoles
Liquid Oxygen
Soft Ferro
large
Strong temporary Attraction
Alignment of magnetic ‘domains’
Refrigerator
Hard Ferro
Strong Permanent Magnetization
Iron, Neodynium

43. D

44. A

45. B