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Page 1. The approach of the magnet makes the B field inside the 3.0 cm diameter loop go from.025 T to.175 T in.0035 s. What is the EMF, direction of the.

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Presentation on theme: "Page 1. The approach of the magnet makes the B field inside the 3.0 cm diameter loop go from.025 T to.175 T in.0035 s. What is the EMF, direction of the."— Presentation transcript:

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2 The approach of the magnet makes the B field inside the 3.0 cm diameter loop go from.025 T to.175 T in.0035 s. What is the EMF, direction of the current, and which electrode is + (current flows out of it).030 V, acw, A N S AB

3 Loop Rotating in B field (show)  = -N d BAcos   t

4 An AC Arc welder can deliver 550 Amps of current. If it draws 18 amps from the wall at 120 VAC, what is the delivered voltage? If the primary has 1200 windings, how many does the secondary have? 3.9 V, 39

5 A transformer has 120 primary windings, and 2400 secondary windings. If there is an AC voltage of 90. V, and a current of 125 mA in the primary, what is the voltage across and current through the secondary? 1800 V, 6.25 mA Solution This one steps up V = 90*(2400/120) = 1800 V Current gets less: Power in = power out (Conservation of energy) IV = IV (0.125 A)(90. V) = (I)(1800) = A = 6.25 mA

6 If you transmit W at 120 V on wires that have a resistance of 2.0 ohms, what power is lost? If you transmit W at 1200 V on wires that have a resistance of 2.0 ohms, what power is lost? 140 W, 1.4 W Use P = IV, so I = P/V, and then P = I 2 R for power lost in each case…..

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8 726,000 m/s W  V =  E p /q,  E p =  Vq = 1 / 2 mv 2  V = 1.50 V, m = 9.11x kg, q = 1.602x C v = = 726,000 m/s Brennan Dondahaus accelerates an electron (m = 9.11x kg) through a voltage of 1.50 V. What is its final speed assuming it started from rest?

9 If the electron is going 1.75 x 10 6 m/s, and the magnetic field is T, what is the radius of the path of the electron? 7.7 cm e- x x x x x m = 9.11 x kg q = x C F = qvBsin  F = ma, a = v 2 /r F = qvBsin  F = ma, a = v 2 /r qvB = mv 2 /r r = mv/qB r = m = 7.7 cm

10 You try this one: Electron going 1.27x10 5 m/s, m = 9.11x kg, B =.0120 T What electric field in what direction will make the electron go straight down the page e- x x x x x x x 1520 N/C to the left

11 If charge carriers were positive: Bottom would be positive

12 If charge carriers were negative: The top would be positive

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14 The approach of the magnet makes the B field inside the 3.0 cm diameter loop go from.025 T to.175 T in.0035 s. What is the EMF, direction of the current, and which electrode is + (current flows out of it).030 V, acw, A N S AB

15 A light bulb has a resistance of Ω, and is hooked up to 240. volts. What current flows through it? A of 200. mA Given: R = V I R = 1200 Ω V = 240 V I = ? I = V/R = 240/1200 = 0.20 A = 200. mA

16 What is the power used by a.135 ohm heating element connected to a 24.0 V source? 4270 W Given: P = IV = I 2 R = V 2 R P = ?? R =.135  V = 24.0 V Use P = V 2 /R P = = 4270 W W

17 The wire moves to the right at 12.5 m/s. What is the EMF generated? Which end of the wire is the + end? 11 V, Bottom B = 1.7 T cm 12.5 m/s  = Bvl  = (1.7 T)(12.5 m/s)(.50 m) = V = 11 V

18 Which way is the current? ACW......

19 Which way is the current? (When does it stop flowing?) CW......

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21 A light bulb has a resistance of Ω, and is hooked up to 240. volts. What current flows through it? A of 200. mA Given: R = V I R = 1200 Ω V = 240 V I = ? I = V/R = 240/1200 = 0.20 A = 200. mA

22 .060 N, Up B =.15 T x x x x x x 20. cm 12v 6.0  Find F and its direction F = IlBsin , I = V/R = 2.0 A F = (2.0 A)(.20 m)(.15 T)sin(90 o ) F =.060 N, Up

23 What is the force acting on a proton moving at 2.5 x 10 8 m/s to the North in a.35 T magnetic field to the East? q = x C F = qvBsin  1.4 x N, Downward F = qvBsin  F = (1.602 x C)(2.5 x 10 8 m/s)(.35 T)sin(90 o ) = 1.4 x N

24 What current in what direction would you need to have a force of 10.0 N to the west in 50.0 cm of wire perpendicular to Earth’s magnetic field of 0.5 x T to the North? 4 x 10 5 A upward F = IlBsin  10.0 N = I(.500 m)(.5 x T)sin(90 o ) I = 4 x 10 5 A ? x N = S (U) N W E S

25 Which way is the force? inta da page I B

26 Which way is the force? down I B x x x x x x

27 Which way is the magnetic field? inta da page I F

28 Which way is the current? outa da page F B


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