{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Physics Lecture 8

# Physics Lecture 8 - i use Right Hand Rule to get direction...

This preview shows page 1. Sign up to view the full content.

Lecture 8: How to make electricity and light I. Faraday’s Law of Induction a. Induction – generating electrical currents with a changing magnetic flux b. Ε = dΦ/dt direction is found with Lenz’s Law i. Approx. ΔΦ/Δt c. Ohm’s Law i. Ε = IR d. Special Cases i. Uniform B, loop in a plane 1. Ε = dΦ/dt = d(NBAcosθ) a. To have E: i. Vary B ii. Vary A iii. Vary θ 2. it is the change in flux that matters not Φ itself e. EXAMPLE: Coil of 100 turns, resistance of 5Ω, radius of 5 cm. Field strength is B=.5T decrease the field to zero in 3 seconds. What is the current i. E = DΦ/dt = 100*π(.05m)^2 (.5/3s) = .13 V ii. I = E/R = .13/5 = 0.026A f. If given B(t) = NBAcos(θ) i. EMF = dΦ/dt = NAcos(θ)dB/dt g. If angle is changing = θ= ωt i. =NBA d/dt(cos(ωt)) II. Lenz’s Law a. There are two magnetic fields i. B ext => causes Faraday’s Effect ii. B int => field produced by the induced current b. If the flux is increasing then the internal field is opposite the external c. If the flux is decreasing the internal is in the same direction as the external
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: i. use Right Hand Rule to get direction of I III. jumping ring Demo a. increase the magnetic field – ring jumps upward i. the field goes up through the ring creating a magnet with a south pole at the bottom IV. Eddy Currents and Magnetic Braking a. Swirling currents in metal plate b. Magnetic force opposes velocity to create braking V. Maxwell’s Equations and Electromagnetic Waves a. Faraday changing B produces E b. Maxwell changing E produces B i. Equations are in integral form (not responsible for them) ii. Possible to make a wave of electric and magnetic fields iii. V propegation of EM wave = 3.0 x 10 8 m / s 1. LIGHT IS AN ELECTROMAGNETIC WAVE iv. Led to the invention of radio waves UNIT 2: Induction, Waves & Light Faraday’s Effect – induced emf Ε = dΦ/dt Φ m = NB dot A = NBAcosθ Ohm: E = IR Lenz’s Law Induced current flows to set up induced field (B ind ) to oppose the change in Φ m A θ B...
View Full Document

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern