Question

Will the bulb in the two circuits glow with the same brightness?
A. Yes
B. No, increased brightness in parallel connection
C. No, decreased brightness in parallel connection
D. Data insufficient

Answer 1

Hint: Use the expression for Ohm’s law which shows that the net potential difference across the ends of the circuit remains the same. Consider two random circuits of series and parallel arrangement and check the effect of the different arrangement of the bulbs on the currents and hence on intensity and brightness of the bulb.

Formula used:
The expression for Ohm’s law is given by
\[V = IR\] …… (1)
Here, \[V\] is the potential difference across the ends of the conductor, \[I\] is the current in the conductor and \[R\] is the resistance of the conductor.

Complete answer:
In an electric bulb, there is a wire of high resistance which converts the electrical energy supplied to it in the light energy. Hence, when electric current is passed through a bulb, it glows. If the electric current decreases then the brightness of the bulb decreases and vice versa.

To check whether the bulb connected in two circuits glows with the same brightness or not, let us assume two different circuits.Consider in the first circuit there are three bulbs connected in series and in the other circuit there are three bulbs connected in parallel.The circuit with three bulbs connected in series is the same as the circuit with three resistors connected in series.

Hence, the net resistance in this first circuit is thrice the resistance of the one bulb. In order to maintain the potential difference across the ends of the circuit, the current in the circuit decreases to one third of the initial value. Thus, the intensity and hence brightness of the bulb decreases.The circuit with three bulbs connected in parallel is the same as the circuit with three resistors connected in parallel.

Hence, the net resistance in this first circuit is less than the bulb with the least resistance. In order to maintain the potential difference across the ends of the circuit, the current in the circuit increases as that of its initial value. Thus, the intensity and hence brightness of the bulb increases.But in the question, we have not given any information about the arrangement of the bulbs in the two circuits. So, we cannot choose the correct option due to insufficient data.

Hence, the correct option is B.

Note: The students may consider any type of arrangement of the bulb to prove that the current on the parallel arrangement of the bulbs is more than in series arrangement of the bulb. This is because there is no arrangement of the bulbs mentioned in the question. Hence, the ultimate answer of this question is option D. One can also directly say that data is insufficient instead of explaining all the things.