Such an oil drop falls 4.0 × 10−15 ?є of , is held stationary when an electric field is applied between the two horizontal plates. If the drop carries six electric charges each of value 1.6 × 10−19 ?, calculate the value of the electric field strength.

Air is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. air enters the heat exchanger at 95 kpa and 20°c at a rate of 0.6 m^3/s. the combustion gases (cp = 1.10 kj/kg°c) enter at 160°c at a rate of 0.95 kg/s and leave at 95°c. determine the rate of heat transfer to the air and its outlet temperature.