Answer
The correct answer is:
C. $~~P \gt Q \gt T \gt R = S$
Work Step by Step
The power dissipated by each bulb is: $P = \frac{V^2}{R} = I^2~R$
The brightness depends on the power that is dissipated.
All the current passes through bulb P, so bulb P is the brightest.
The potential difference across bulb Q is greater than the potential difference across bulb R, bulb S, and bulb T. Therefore, bulb Q is the second brightest.
The current through bulb T is equal to the sum of the current through bulb R and bulb S, Therefore, bulb T is the third brightest.
Since bulb R and bulb S are in parallel, the potential difference across bulb R and bulb S is the same. Then bulb R and bulb S are equally bright.
The correct answer is:
C. $~~P \gt Q \gt T \gt R = S$
