Find the potential difference between points $A$ and $B$ in the following circuit. (in $V$)

Two equal resistances when connected in series to a battery,consume electric power of $60 \, W$. If these resistances are now connected in parallel combination to the same battery,the electric power consumed will be .............. $W$.

Two wires of resistances $R_1$ and $R_2$ have temperature coefficients of resistance $\alpha_1$ and $\alpha_2$ respectively. If these are joined in series,the effective temperature coefficient of resistance is:

In how much time will one litre of ${H_2}$ be collected by a $5\, A$ current? (Given: $Z = 1 \times {10^{ - 8}}\,kg/C$ and density of ${H_2} = 0.09\,kg/{m^3}$)

$A$ torch battery consists of two cells of $1.45\,V$ and an internal resistance of $0.15\,\Omega$ each. Both cells send current through the filament of a lamp having a resistance of $1.5\,\Omega$. The value of the current will be ....... $A$.

Two resistances of $400 \Omega$ and $800 \Omega$ are connected in series with a $6 \text{ V}$ battery of negligible internal resistance. $A$ voltmeter of resistance $10000 \Omega$ is used to measure the potential difference across the $400 \Omega$ resistor. The error in the measurement of potential difference in volts is approximately: