Question

All the bulbs and cells used in the circuits are identical. If the switches are turned ON, in which of the following options will the bulb(s) be the brightest?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Among the given circuits, the circuit in which a single bulb has been connected to two cells that are in series, will have the brightest bulb.
In a series circuit, the same amount of current flows through all the components placed in it. Therefore the bulb here is getting a power equal to twice that of a single cell.

In the other circuits, there is eiher a single cell or two cells have been connected in parallel. In parallel connection of cells, each cell has its own independent path for the flow of electric current. Therefore, a bulb connected to two cells in parallel is as bright as a bulb connected to a single cell. Furthermore, when two bulbs are connected in series, the power supplied by the cells gets equally distributed among the two bulbs. Therefore, the bulbs in all the other three circuits are only getting the power of a single cell or half a cell.