$A$ coil develops heat of $800 \, cal/sec$ when $20 \, V$ is applied across its ends. The resistance of the coil is .............. $\Omega$ $(1 \, cal = 4.2 \, J)$.

If voltage across a bulb rated $220 \text{ V} - 100 \text{ W}$ drops by $2.5\%$ of its rated value,the percentage of the rated value by which the power would decrease is ............... $\%$

Two identical electric lamps marked $500\, W, 220\, V$ are connected in series and then joined to a $110\, V$ line. The power consumed by each lamp is

$A$ constant voltage is applied between the two ends of a metallic wire. If both the length and the radius of the wire are doubled, the rate of heat developed in the wire

$A$ $10\, V$ storage battery of negligible internal resistance is connected across a $50\,\Omega$ resistor. How much heat energy is produced in the resistor in $1$ hour? (in $J$)

Four wires of the same diameter are connected in turn between two points,maintained at a constant potential difference. Their resistivities and lengths are: $\rho$ and $L$ (wire $1$),$1.2\rho$ and $1.2L$ (wire $2$),$0.9\rho$ and $0.9L$ (wire $3$),and $\rho$ and $1.5L$ (wire $4$). Rank the wires according to the rates at which energy is dissipated as heat,greatest first.