A cylindrical resistor element on a circuit board dissipates 0.6 W of power. The resistor is 1.5 cm long, and has a diameter of 0.4 cm. Assuming heat to be transferred uniformly from all surfaces, determine

(a) the amount of heat this resistor dissipates during a 24-hour period,
(b) the heat flux, and
(c) the fraction of heat dissipated from the top and bottom surface

a. 51.84Kj

b. 2808.99 W/m^2

c. 11.75%

Explanation:

Amount of heat this resistor dissipates during a 24-hour period

= amount of power dissipated * time

= 0.6 * 24 = 14.4 Watt hour

(Note 3.6Watt hour = 1Kj )

=14.4*3.6 = 51.84Kj

Heat flux = amount of power dissipated/ surface area

surface area = area of the two circular end  + area of the curve surface

= 2.136 *10^-4

Heat flux = = 2808.99

fraction of heat dissipated from the top and bottom surface

=11.75%

energy can cross the boundaries of a closed system in the form of heat and mass

explanation: