Question

which bulb in the diagram will be the brightest?
a
b
they will be the same.
c

Explanation:

Step1: Recall parallel circuit voltage rule

In a parallel circuit, the voltage across each branch is equal to the source voltage, so $V_A = V_B = V_C = V_{source}$.

Step2: Relate brightness to power

The brightness of a bulb depends on its power output, given by $P = \frac{V^2}{R}$ (assuming all bulbs have identical resistance $R$).

Step3: Compare power of each bulb

Since $V$ and $R$ are the same for all bulbs, $P_A = P_B = P_C = \frac{V_{source}^2}{R}$. Equal power means equal brightness.

Answer:

They will be the same.