Electromagnetic Induction Chapter 33 Electromagnetic Induction Phys 133 -- Chapter 33

Demo Faraday Phys 133 -- Chapter 33

Some experiments Phys 133 -- Chapter 33

Motional emf Phys 133 -- Chapter 33

Motional emf (cont.) Reach equilibrium Phys 133 -- Chapter 33

Problem 33.1 A potential difference of 0.050 V is developed across a 10-cm long wire as it moves through a magnetic field at 5.0 m/s. The magnetic field is perpendicular to the wire axis. What are strength and direction of field? Phys 133 -- Chapter 33

Problem 33.1 (ans) At equilibrium Fm Fe Out of page Phys 133 -- Chapter 33

Induced current --moving charges in B field, force --> current --current-carrying wire in field, force Phys 133 -- Chapter 33

Do workbook 33.1 Phys 133 -- Chapter 33

Eddy currents Phys 133 -- Chapter 33

Do workbook 33.2 & 4 Phys 133 -- Chapter 33

Eddy currents (cont.) Phys 133 -- Chapter 33

Demo eddy currents Phys 133 -- Chapter 33

Do workbook 33.5 & 7 33.5 & 7 Phys 133 -- Chapter 33

Magnetic flux Phys 133 -- Chapter 33

Do workbook 33.9 & 11 Phys 133 -- Chapter 33

Lenz’s law There is an induced current in a closed, conducting loop if and only if the magnetic flux through the loop is changing. The induced current creates an induced magnetic field which opposes the change in flux. --changing flux produces induced current --induced current creates induced field --induced field opposes the change Phys 133 -- Chapter 33

Do workbook 33.12, 13 & 19 Phys 133 -- Chapter 33

Problem 33.9 The current in the solenoid is decreasing. The solenoid is surrounded by a conducting loop. Is there a current in the loop? If so, is the current in the loop cw or ccw? Phys 133 -- Chapter 33

Problem 33.9 (ans) Find change in flux Initially   ∆ B1  Change in flux to left Find induced field later Induced field points to right B2  Find induced current Induced current is clockwise from behind Phys 133 -- Chapter 33

Induced fields field is there independent of wire Phys 133 -- Chapter 33

Faraday’s law --law of nature --usually helpful -field can change -area can change -both can change Phys 133 -- Chapter 33

Do workbook 33.21 Phys 133 -- Chapter 33

Problem 33.12b The loop is being pushed out of the 0.20 T magnetic field at 50 m/s. The resistance of the loop is 0.20 . What are the direction and magnitude of current in the loop? Phys 133 -- Chapter 33

Problem 33.12b (ans) L w Counter-clockwise Phys 133 -- Chapter 33

Problem 33.35 Two 20-turn coils are tightly wrapped on the same 2.0-cm-diameter cylinder with 1.0-mm-diameter wire. The current through coil 1 is shown. A positive current is into the page at the top of the loop. Determine the current in coil 2 as current vs. time t = 0 s to 0.4 s. (Assume field of coil 1 passes completely through coil 2. 0.1 0.3 Phys 133 -- Chapter 33

Problem 33.35 (ans) (+) I1 d2/dt B1 2 2 I2 Phys 133 -- Chapter 33

(+) I1 I2 Problem 33.35 (ans) Right to left through resistor Phys 133 -- Chapter 33

Generator Phys 133 -- Chapter 33

Transformer Phys 133 -- Chapter 33

Coulomb and non-Coulomb electric fields Phys 133 -- Chapter 33

Maxwell and induced magnetic field -symmetric in E and B Phys 133 -- Chapter 33

E & M equations Phys 133 -- Chapter 33

Maxwell’s equations Phys 133 -- Chapter 33

Maxwell-no charges or current +math Light is an E&M wave!!! Phys 133 -- Chapter 33

EM waves Phys 133 -- Chapter 33

Problem 33.49 A U-shaped conducting rail that is oriented vertically in a horizontal magnetic field. The rail has no electrical resistance and does not move. A slide wire with mass m and resistance R can slide up and down without friction while maintaining electrical contact with the rail. The slide wire is release from rest. Describe the motion of the slide wire. Find the terminal velocity of the slide wire Phys 133 -- Chapter 33