Question

The ${B_1}$​, ${B_2}$​ and ${B_3}$​ are three identical bulbs connected as shown in Figure. When all the three bulbs glow, a current of $3A$ is recorded by the ammeter $A$.What happens to the reading of ${A_1}$​, ${A_2}$​, ${A_3}$​ ​ and $A$ when the bulb ${B_2}$​ gets fused?

Answer 1

To solve this question, we need to determine first the type of connection in which the three bulbs are connected. From the figure, it is clear that all the three bulbs are connected by parallel connection. Therefore, we need to consider how the current is distributed in parallel with the help of which we can finally determine the effect on the readings of all four ammeters.

Complete answer:
It is clearly seen from the figure that three bulbs are connected in parallel connection. Therefore, the current flowing through each bulb will be one third of the total current. This is because of the fact that in parallel connection, total current is divided into equal amounts among the number of resistances.

Here, it is given that the total current of $3A$ is recorded by the ammeter$A$ when all the bulbs are glowing. Therefore, in this condition, the readings in all three ammeters ${A_1}$​, ${A_2}$​ and ${A_3}$​ will be $1A$.Now, let us consider the case when the bulb ${B_2}$​ gets fused. In this condition, there will be no current passing through ammeter ${A_1}$.

Therefore it will show zero reading. Because of the parallel connection, there will not be any change in the readings of the other two ammeters. Therefore, ${A_2}$​ and ${A_3}$​ both will show the readings of $1A$. Finally as the ammeter $A$ is showing the total current passing through the circuit, it will show the reading of the total of current passing through${A_2}$​ and ${A_3}$​ which will be $2A$.

Note: In this problem, we have seen that in parallel connection, when one off the appliances gets fused, the others remain unaffected. Whereas, in series connection, all the appliances stop working when one of them gets fused. This is one of the reasons why our home appliances are connected in parallel and not in series.