Name 2017 vB Part 1 -Multiple Choice- 5 pts each 1. The figure shows a steady el

Question

Name 2017 vB Part 1 -Multiple Choice- 5 pts each 1. The figure shows a steady electric current passing through a wire with a narrow region. What happens to the drift velocity of the moving charges as they go from region A to region B and then to region C? a) The drift velocity decreases from A to B and increases from B to C. b) The drift velocity increases from A to B and decreases from B to C. c) The drift velocity remains constant d) The drift velocity increases all the time. e) The drift velocity decreases all the time. 2. Two identical resistors of resistance R-24 and a variable resistor Rx are connected to an ideal battery of voltage V as shown in the figure. What should be the value of the variable resistance Rx to make the voltage across the two parallel resistors equal to V/S .t A) 8.0 B)4.0 C) 16 D)40 E) 24

Explanation / Answer

1. Vd = I / (n A q)

n, q and I are same for all three section.

A decreases then Vd increases.

Ans(b)

2. VR = V - (V/5) = 4 V / 5

R / R' = (4 V/ 5) / (V / 5)

R / R' = 4

R = 4 (R Rx) / (R + Rx)

R + Rx = 4 Rx

Rx = R/3 = 8 ohm

Ans(A)

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