HW7%20solutions

# HW7%20solutions - Physics 204, morning summer 2008 Homework...

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Physics 204, morning summer 2008 Homework 7 solutions Chapter 21 Problems 49,72, 28, 29 Chapter 22 Problems 2 49. SSM REASONING AND SOLUTION The current associated with the lightning bolt is 4 15 C q Δ 3 1.0 10 A 1.5 10 s I t == = × Δ × The magnetic field near this current is given by () ( ) 74 41 0 T m / A 1 . 0 1 0 A I π μ ×⋅ × 5 0 8.0 10 T 22 2 5 m B r ππ = × 72. REASONING AND SOLUTION Let the current in the left hand wire be labeled I 1 and that in the right hand wire I 2 . a. At point A : B 1 is up and B 2 is down , so we subtract them to get the net field. We have B 1 = μ 0 I 1 /(2 d 1 ) = μ 0 (8.0 A)/[2 (0.030 m)] B 2 = μ 0 I 2 /(2 d 2 ) = μ 0 (8.0 A)/[2 (0.150 m)] So the net field at point A is 4.3 10 T 5 × B A = B 1 & B 2 = b. At point B : B 1 and B 2 are both down so we add the two. We have B 1 = & 0 (8.0 A)/[2 (0.060 m)] B 2 = & 0 (8.0 A)/[2 (0.060 m)] So the net field at point B is 5.3 10 T 5 × B B = B 1 + B 2 = 28. REASONING A magnetic field exerts no force on a current-carrying wire that is directed along the same direction as the field. This follows directly from sin FI L B θ = (Equation 21.3), which gives the magnitude

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## This note was uploaded on 10/04/2009 for the course PHYS 750:204 taught by Professor Rollino during the Spring '09 term at Rutgers.

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HW7%20solutions - Physics 204, morning summer 2008 Homework...

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