How many $sec$ are required to raise the temperature of $1\, litre$ of water from $20\,^oC$ to $40\,^oC$ using an $836\, W$ heater?

Heat energy at a constant rate is supplied to two substances $P$ and $Q$. If the variation of temperature $(T)$ of the substances with time $(t)$ is as shown in the figure,then select the correct statement.

Is the specific heat of water greater than that of sand?

The figure below shows the variation of specific heat capacity $(C)$ of a solid as a function of temperature $(T)$. The temperature is increased continuously from $0$ to $500 \ K$ at a constant rate. Ignoring any volume change,which of the following statement$(s)$ is (are) correct to a reasonable approximation?
$(A)$ The rate at which heat is absorbed in the range $0-100 \ K$ varies linearly with temperature $T$.
$(B)$ Heat absorbed in increasing the temperature from $0-100 \ K$ is less than the heat required for increasing the temperature from $400-500 \ K$.
$(C)$ There is no change in the rate of heat absorption in the range $400-500 \ K$.
$(D)$ The rate of heat absorption increases in the range $200-300 \ K$.

$100 \ g$ of water is heated from $30^\circ C$ to $50^\circ C$. Ignoring the slight expansion of the water,the change in its internal energy is .......$kJ$ (specific heat of water is $4184 \ J/kg/K$):

Is the molar specific heat of a solid a constant value? Explain.