## 20160614

### Physics quiz question: ammeter reading, connected in series with voltmeter

Physics 205B Quiz 5, spring semester 2016
Cuesta College, San Luis Obispo, CA

An ideal 3.2 V emf source is connected to an ideal voltmeter and ammeter, a light bulb, and a resistor. The light bulb is lit. The ammeter reading is:
(A) zero.
(B) some finite, non-zero value below 0.67 A.
(C) exactly 0.67 A.
(D) some finite value above 0.67 A.
(E) ∞.

Correct answer (highlight to unhide): (A)

An ideal ammeter has zero resistance, but it is connected in series to an ideal voltmeter, which has an infinite resistance. Thus no current will flow through the upper loop of this circuit, such that the ammeter will read zero.

(Response (C) is the amount of current flowing through the emf, light bulb, and resistor in the lower loop of this circuit.)
Sections 30882, 30883
Exam code: quiz05Tt1p
(A) : 17 students
(B) : 5 students
(C) : 11 students
(D) : 4 students
(E) : 1 student

Success level: 45%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.26