Pressure is directly proportional to the area of contact.

Heat produced in any resistor is directly proportional to the square of the _____________ passing through the resistor.

The speed of sound is directly proportional to the square root of the _________ .

Express each of the following physical statements in the form of differential equation. (iii) For a certain substance, the rate of change of vapor pressure P with respect to temperature T is proportional to the vapor pressure and inversely proportional to the square of the temperature.