The effective resistance between $P$ and $Q$ for the following network is

Five identical resistors each of resistance $R=1500 \Omega$ are connected to a 300 V battery as shown in the circuit. The reading of the ideal ammeter $A$ is

Two cells of internal resistances $r_1$ and $r_2$ and of same emf are connected in series, across a resistor of resistance $R$. If the terminal potential difference across the cells of internal resistance $r_1$ is zero, then the value of $R$ is

The $I-V$ graphs for two different electrical appliances $P$ and $Q$ are shown in the diagram: If $R_P$ and $R_Q$ be the resistances of the devices, then