Question

Why are identical bulbs arranged in a series circuit with a battery less bright than those arranged in a parallel circuit with the battery?

Answer 1

Explanation:

Resistors connected in series obey the following equation:

$R_{\rm eq} = R_1 + R_2 + R_3 + ...$

Resistors connected in parallel obey the following equation:

$\frac{1}{R_{\rm eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + ...$

The total current of the circuit will obey the Ohm's Law: V = IR. And the current will be divided across the resistors (bulbs) depending on their resistances. So, if a bulb has a higher resistance, then its current will be lesser, and it will be less bright. If a bulb has a lower resistance, then its current will be higher, and it will be brighter.

According to the above resistances connected in series and parallel, clearly, the resistances (bulbs) connected in series will have more resistance in total, and therefore less current will flow across them, and they will be less bright.