Two identical cells gave the same current through an external resistance of $2 \Omega$ regardless whether the cells are grouped in series or parallel. The internal resistance of the cells is

The charge $q$ (in coulomb) passing through a $10 \Omega$ resistor as a function of time $t$ (in second) is given by $q=3 t^2-2 t+6$. The potential difference across the ends of the resistor at time $t=5 \mathrm{~s}$ is

A cell of emf 1.2 V and internal resistance $2 \Omega$ is connected in parallel to another cell of emf 1.5 V and internal resistance $1 \Omega$. If the like poles of the cells are connected together, the emf of the combination of the two cells is

Five equal resistances each $2 R$ connected as shown in figure. A battery of $V$ volts connected between $A$ and $B$. Then, current through $F C$ is