If a battery of voltage V is connected across terminals I of the black box as shown in figure, an ideal voltmeter connected to terminals II gives a reading of V/2. If the same battery is connected to terminals II, an ideal voltmeter across terminals I reads V. Assuming that the black box consists only resistances, which of the following can be the possible combinations?
Select all that apply

Question

If a battery of voltage V is connected across terminals I of the black box as shown in figure, an ideal voltmeter connected to terminals II gives a reading of V/2. If the same battery is connected to terminals II, an ideal voltmeter across terminals I reads V. Assuming that the black box consists only resistances, which of the following can be the possible combinations?

Select all that apply

G1 Physics · Accepted Answer

Treat the voltmeter as an open circuit. Only arrangements A and D give V/2 at terminal II when the battery is applied at terminal I, and V at terminal I when the battery is applied at terminal II. Hence A,D.