20110404

Physics quiz question: potential differences for resistors in series

Physics 205B Quiz 4, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.21.

Consider a two ideal batteries and two resistors connected in series as shown at right. Which resistor has the largest potential difference?
(A) 3.0 Ω resistor.
(B) 4.0 Ω resistor.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer: (B)

Due to Kirchhoff's junction rule, since there are no junctions in this simple series circuit, the batteries and resistors must all have the same amount of current flowing through them.

However, from Ohm's law:

delta(V) = I*R,

since the 4.0 Ω resistor has a higher resistance than the 3.0 Ω resistor, then it will have a higher potential difference than the 3.0 Ω resistor.

Student responses
Section 30822
Exam code: quiz04t4c0
(A) : 5 students
(B) : 3 students
(C) : 0 students
(D) : 0 students

Success level: 38%
Discrimination index (Aubrecht & Aubrecht, 1983): 1.00

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