Physics quiz question: current at parallel-series junction

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

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Comprehensive Problem 18.112.

Consider an ideal 6.0 V emf source connected to a 2.5 Ω resistor, and two 1.2 Ω light bulbs, as shown at right. Which resistive circuit element has the most current flowing through it?
(A) 2.5 Ω resistor.
(B) Light bulb 1.
(C) Light bulb 2.
(D) (There is a tie between two of the above choices.)
(E) (There is a three-way tie.)
(F) (Not enough information is given.)

Correct answer: (B)

Due to Kirchhoff's junction rule, the current flowing through bulb 1 is the sum of the current flowing through the 2.5 Ω resistor and the current flowing through bulb 2.

Student responses
Section 30822
Exam code: quiz04t4c0
(A) : 0 students
(B) : 2 students
(C) : 2 students
(D) : 3 students
(E) : 1 student

Success level: 25%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50