Which of the following statements is true?

Two resistances $X$ and $Y$ are connected in the two gaps of a meter bridge,and the null point is obtained at $20 \text{ cm}$ from the zero end. When a resistance of $20 \text{ } \Omega$ is connected in series with the smaller of the two resistances $X$ and $Y$,the null point shifts to $40 \text{ cm}$ from the left end. The value of the smaller resistance in ohms is:

Two capacitors $C_1$ and $C_2$ in a circuit are joined as shown in the figure. The potential of point $A$ is $V_1$ and that of $B$ is $V_2$. The potential of point $D$ will be

When a current of $2\, A$ flows in a battery from negative to positive terminal,the potential difference across it is $12\, V$. If a current of $3\, A$ flows in the opposite direction,the potential difference across the terminals of the battery is $15\, V$. The $emf$ of the battery is ................ $V$.

Which of the following organelles is $NOT$ a part of the endomembrane system?

For preparing a $0.1 \, N$ solution of a compound from its impure sample,of which the percentage purity is known,the weight of the substance required will be