PHYS1120 Exam III review
Things to remember for PHYS1110: algebra, trig (sin, cos, ..)
vector math, especially vector addition, Fnet = ma problems, free-body diagrams
Exam1 and Exam2 Material : E-fields, Gauss's Law, voltage, capacitors, circuits.
Last part of Chapter 26 : RC circuits
• Voltage across a capacitor is always 
• An uncharged capacitor has ΔV= 0 , acts like a wire, as short (does not resist the flow of current).
• A fully charged capacitor has I = 0, acts like an open switch.
• time constant is 
Ch. 27 Magnetic fields
• 
This is the definition of B .
• When both E-field and B-field are present: 
• Motion of charge in magnetic field and in velocity selector.
• 
force and torque on a current loop
Ch. 28 Sources of Magnetic fields
• Currents cause magnetic fields (B-fields)
• Biot-Savart Law: 
(Know what all the symbols mean)
• Ampere's Law: 
Be able to use Ampere to derive
▪ B-field outside long straight wire: 
▪ B-field inside long wire of radius R: 
▪ B-field inside solenoid: 
(No need to memorize these formulas; know how to derive them)
• "right-hand rule 2": point thumb in direction of straight thing, fingers curl in sense of circular thing.
• B-field is a vector: 
• parallel currents attract; anti-parallel currents repel
• Gauss's Law for B-fields: 
Magnetic monopoles do not exist.
• field of a solenoid, permanent magnet acts like solenoid
Ch. 29 Faraday's Law
• Faraday's Law: An emf (= battery voltage) is caused by a changing magnetic flux:
magnetic flux 
Be able to use Faraday's Law to derive E-field inside or outside a solenoid.
• Lenz's Law: Iinduced creates Binduced in direction that opposes the change in flux.
• Motors and generators
• Eddy current forces always oppose the motion
To prepare for any exam:
• Study my online lecture Notes.
• Review Concept Tests, MP problems, and Tutorial HW. (Read question and try to remember reasoning that gets to the answer)
• Prepare your formula sheet. Prioritize: which are the important equations?
• Take the practice exam.
• It is no good to memorize answers. You have to understand and remember how you got the answers.