In the diagrams, all light bulbs are identical and all emf devices are identical. In which circuit (I, II, III, IV, V) will the bulbs be dimmest?
A) I
B) II
C) III
D) IV
E) V

Question

In the diagrams, all light bulbs are identical and all emf devices are identical. In which circuit (I, II, III, IV, V) will the bulbs be dimmest? 
A) I 
B) II 
C) III 
D) IV 
E) V

Quizplus · Accepted Answer

In circuit IV, the bulbs will be dimmest because the emf devices are arranged in series, which will cause a larger voltage drop across each device and result in lower voltage supplied to the bulbs. In circuits I, II, and III, the emf devices are arranged in parallel, which will result in a higher voltage supplied to the bulbs and therefore brighter bulbs. Circuit V is a combination of series and parallel arrangements, but the emf devices have the same potential difference across them, meaning that the bulbs will be equally bright in all branches.

In the Diagrams, All Light Bulbs Are Identical and All