Physics 212 Exam 2 Sample 1

# Physics 212 Exam 2 Sample 1 - Physics 212 Midterm 2 Form A...

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Physics 212 Midterm 2 Form A 1. A wire contains a steady current of 2 A. The charge that passes a cross section in 2 s is: A. 3.2 × 10 -19 C B. 6.4 × 10 -19 C C. 1 C D. 2 C E. 4 C 2. In a Physics 212 lab, Jane measures the current versus voltage characteristics for two nichrome wires and makes the graph shown. The wires are of the same diameter but have different lengths . Which of the following statements is correct? 3. The current density across a cylindrical conductor of radius R varies according to the equation J = J 0 ( r / R ), where r is the distance from the central axis. Thus, the current density is zero at the axis ( r = 0) and increases linearly to J 0 at the surface ( r = R ). Calculate the current in terms of J 0 and R . A. i = ( π R 2 J 0 )/2 B. i = (2 π R 2 J 0 )/3 C. i = ( π R 2 J 0 )/6 D. i = ( π R 3 J 0 )/3 E. i = ( π R 3 J 0 )/6 4. A wire is 1 m long and 1 × 10 -6 m 2 in cross-sectional area. When connected to a potential difference of 2 V, a current of 4 A exists in the wire. The resistivity of the wire material is: Page 1

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