The meter bridge shown in the balance position with P Q = l_1 l_2 ....

$$\text{ For balanced position in a meterbridge }$$
$$\text{ Now, if position of } \mathrm{G} \text{ and cell is interchanged, }$$
The balance condition still remains the same if the jockey points as the same point as given in the initial condition, for which there is no deflection in the galvanometer or no current will be drawn from the cell. Thus, the bridge will work as usual and balance condition is same, $P / Q=l_1 / l_2$