Two identical heater filaments are connected first in parallel and then in series. At the same applied voltage, the ratio of heat produced in same time for parallel to series will be:

The $H$ amount of thermal energy is developed by a resistor in $10\,s$ when a current of $4\,A$ is passed through it. If the current is increased to $16\,A$, the thermal energy developed by the resistor in $10\,s$ will be $........\,H$

$(a)$ Consider circuit in figure. How much energy is absorbed by electrons from the initial state of no current (ignore thermal motion) to the state of drift velocity ?

$(b)$ Electrons give up energy at the rate of $R{I^2}\;$ per second to the thermal energy. What time scale would number associate with energy in problem $(a)$ ? $n = no$ of electron/volume $ = {10^{29}}{m^{ - 3}}$, length of circuit $= 10$ $cm$, cross-section $=$ $A = $ ${\left( {1\,mm} \right)^2}$

A resistor develops $300 \,J$ of thermal energy in $15 \,s$, when a current of $2\, A$ is passed through it. If the current increases to $3 \,A$, the energy developed in $10\,\,s$  is........$J.$

Figure shows three similar lamp. $L_1,L_2$ and $L_3$ connected across a power supply. If the lamp $L_3$ fuses, how will the light emitted by $L_1$ and $L_2$ change ?

Four identical electrical lamps are labelled $1.5\,V$, $0.5\,A$ which describes the condition necessary for them to operate at normal brightness. A $12\,V$ battery of negligible internal resistance is connected to lamps as shown, then