$A$ button battery is rated $3 \,V$ and $225 \,mAh$. $A$ cricket ball (mass $= 0.163 \,kg$) having energy equal to that stored in the battery will have a speed closest to ............ $\,m/s$.

The resistor of resistance $R$ is connected to a $25\, V$ supply and the heat produced in it is $25\, J/s$. The value of $R$ is .......... $\Omega$.

Two electric bulbs have resistances in the ratio $1 : 2$. If they are connected in parallel to a constant voltage source,the ratio of power dissipated in them will be:

$A$ rise of temperature of $4\,^oC$ is observed in a conductor by passing a current. If the current is tripled,the rise in temperature will be .............. $^oC$.

$A$ hot electric iron has a resistance of $80\,\Omega$ and is used on a $200\,V$ source. The electrical energy spent,if it is used for two hours,will be ........... $Wh$.

The ratio of cross-sectional areas of two conducting wires made up of the same material and having the same length is $1 : 2$. What will be the ratio of heat produced per second in the wires,when the same current is flowing in them?