If `X, Y` and `Z` in figure are identical lamps, which of the following changes to the brightness of the lamps occur when switch `S` is closed?

Options

A. `X` stays the same, `Y` decreases
B. `X` increase, `Y` decreases
C. `X` increase, `Y` stays the same
D. `X` decrease, `Y` increase

Answer

B

Explanation

(b) `P = (V^(2))/(R )` Initially, `I = (V)/(2R)`
Power across `P_(x) = P_(Y) = ((epsilon^(2))/(4R)) R`
Finally, `I = (2V)/(3R)`, Power `P_(X) = (4 V^(2))/(9 R)`, `P_(Y) = P_(z) = (2V^(2))/(9R)`
Hence `P_(x)` increases, `P_(y)` decreases.