The power that a resistor must dissipate is jointly proportional to the square of the current flowing through the resistor and the resistance of the resistor. If a resistor needs to dissipate 63 watts of power when 3 amperes of current is flowing through the resistor whose resistance is 7 ohms comma find the power that a resistor needs to dissipate when 9 amperes of current are flowing through a resistor whose resistance is 5 ohms.