## 20170320

### Physics quiz question: ammeter readings in circuit perimeter

Physics 205B Quiz 5, spring semester 2015
Cuesta College, San Luis Obispo, CA

Two ideal ammeters are connected to circuit with a switch, an ideal 1.5 V emf source, a light bulb and a resistor, as shown at right. While the switch remains open, the __________ ammeter has a higher reading.
(A) top.
(B) bottom.
(C) (There is a tie, where both ammeters have a zero reading.)
(D) (There is a tie, where both ammeters have a finite, non-zero reading.)
(E) (Not enough information is given.)

Correct answer (highlight to unhide): (C)

While the switch remains open, the emf is isolated from the circuit, which is completed around its perimeter with just a light bulb, resistor, and two ammeters without any source of emf. Thus no current will flow through outer perimeter of this circuit, such that both ammeters will read zero.

Sections 30882, 30883
Exam code: quiz05aL7y
(A) : 2 students
(B) : 3 students
(C) : 37 students
(D) : 5 students

Success level: 79%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.32