Question

A circuit is connected as shown. All light bulbs are identical. When the switch in the circuit is closed illuminating bulb #4, which other bulb(s) also become brighter?

(A) Bulb #1 only 

(B) Bulb #2 only 

(C) Bulbs #2 and #3 only 

(D) Bulbs #1, #2, and #3

(E) None of the bulbs.

Answer 1

The correct option is: (A) Bulb #1 only 

Explanation:

Closing the switch reduces the total resistance of the circuit, increasing the current in the main branch containing bulb 1.