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Unformatted text preview: Solution for Practice Test 7 for Test 3 Solution to Practice Test Problem 7.1(Inductor in Circuit Problem) Problem: A triangular wave signal is applied to an inductor with inductance . 5H . The time dependance of the current is I ( t ) = (0 . 22 A s )t . Calculate the magnitude of the voltage across the inductor at time 3s . Select One of the Following: (aAnswer) . 11V (b) . 33V (c) . 0242V (d) . 0121V Solution The voltage measured across and inductor is given by V = L dI dt = (0 . 5H) d( (0 . 22 A s )t) dt = (0 . 5H)(0 . 22 A s ) = 0 . 11V Total Points for Problem: 3 Points Solution to Practice Test Problem 7.2(What Produces Uniform Field?) Problem: For some application, you are asked to produce a uniform magnetic field (in some region) using equipment you already have in the lab. Which of the following produces a uniform field? Select One of the Following: (a) Annular ceramic magnet (b) Infinite straight wire (cAnswer) Infinite solenoid (d) Loop of wire (e) Finite current element Solution A solenoid produces a uniform magnetic field in its interior. Total Points for Problem: 3 Points Solution to Practice Test Problem 7.3(What makes a Generator Work?) Problem: What is the name of the central physical law explaining the behavior of a generator? Select One of the Following: (a) Lorentz 1 (b) Gauss (c) Ampere (dAnswer) Faraday (e) Murphy Solution Faradays law. Total Points for Problem: 3 Points Solution to Practice Test Problem 7.4(Direction of Induced Current) Problem: A square coil of wire sits in a magnetic field directed as shown. The magnetic field is decreasing in strength. The direction of the induced current is: Select One of the Following: (a) clockwise (bAnswer) counterclockwise (c) zero current Solution The flux out of the page is decreasing, so the induced current will produce a flux out of the page. By the right hand rule, that requires a counterclockwise current. Total Points for Problem: 3 Points Solution to Practice Test Problem 7.5(Force on Stationary Charge) Problem: Calculate the magnitude of the force between a stationary pith ball with charge 1nC and the earths 4 10 5 T field. Select One of the Following: (a) 4 10 13 N (b) 4 10 5 N (c) 4 10 5 N (dAnswer) Solution The magnetic force on a stationary charge is zero. Total Points for Problem: 3 Points 2 Solution to Practice Test Problem 7.6(Proton in Magnetic Field) Problem: A proton ( m p = 1 . 67 10 27 kg , q p = +1 . 6 10 19 C ) is fired into a uniform magnetic field whose direction is perpendicular to the page. The proton follows a circular path through the field as shown. The speed of the proton is 3 10 6 m s and the radius of curvature is 10cm . Calculate the magnitude and direction of the magnetic field....
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 Spring '08
 Stewart
 Physics, Current, Inductance

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