Spring_2010_Exam_2_Form_A

Spring_2010_Exam_2_Form_A - FORM A PHYS 272 Spring 2010...

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1 PHYS 272 Spring 2010 EXAM-II There are two parts to the Exam: nine multiple-choice problems (72 points) and one comprehensive problem to be hand-graded (28 points). All pages are double-sided. The Answer-Sheet is the last page (both multiple-choice and hand-graded). Tear off the last page to be turned in after you finish. Important: Enter your Name, PUID, Signature on the Answer-Sheet. Show your Purdue ID card to the Instructor when turning in the Answer-Sheet. Useful information Current and drift velocity: i nAv = I q nAv = v uE = Biot-Savart for single charge: 0 2 ˆ 4 qv r B r µ π × = Capacitance: 0 / C K As ε = Conductivity and resistance: qnu σ = /( ) RL A = Ohm’s law: V IR ∆= Power: P IV = Lorentz force: F qE qv B =  Magnetic force on current segment: F Il B = ∆× Torque on magnetic dipole: B τµ = × Potential energy of magnetic dipole: UB = −⋅
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FORM A 2 Problem 1 [8 points] Constant current is run through a coil. We cut the coil in half, so that we have two coils, each with half as many turns as the original coil. The same amount of current is run through the coils after the cut. What do you think we would get? (A) Two weaker coils, one with a North pole and the other with a South pole. (B) Two coils of the same strength as before the cut, one with a North pole the other with a South pole. (C) Two weaker coils, each with a North pole and a South pole. (D) Two coils of the same strength as before the cut, each with a North pole and a South pole. (E) Two coils that do not make any magnetic field. (F) None of the above. Problem 2 [8 points] What makes current flow in a circuit? (A) Electrons push each other by collisions through the wire. (B) The electrons are free to move in the wire without colliding with each other. (C) Since there is no friction, no force is needed to keep electrons moving. (D) A nonzero electric field inside the wire keeps the electrons moving. (E) None of the above.
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FORM A 3 Problem 3 [8 points] A proton and an electron are moving at a particular instant as shown in the figure below.
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Spring_2010_Exam_2_Form_A - FORM A PHYS 272 Spring 2010...

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