PRACTICE PROBLEMS MODULE 1 QUESTIONS AND ANSWERS WITH SOLUTIONS 2024/25

A glass window 0.33 cm thick measures 81 cm by 39 cm. How much heat flows through this window per minute if the inside and temperatures differ by 13 C°? - ANSWER 63 kJ/min Heat conducts through a glass window from a warm room to the colder outdoors as shown in the figure. (Q/t) =kA(delta T/L) Q/t = (0.84 W/(m x K)] (0.81 m) (0.39 m)(13 C/.0033m) (60 s/ min) = 63 kJ/ min Estimate the heat required to heat a 0.15-kg apple from 12 degrees (Celsius) to 36 degrees (Celsius). (Assume the apple is mostly water). - ANSWER 15 kJ Q=mcAT = (0.15 kg) 4186 J/ (kg - K)] (36-12°C) = 15 kJ Incandescent lightbulbs heat a tungsten filament to a temperature of about 4580°F, which is almost half as hot as the surface of the sun. What is the temperature in degrees Celsius? - ANSWER 2530 C Tc = 5/9 (4580°F -32°F) = 2527°C = 2530°C For temperatures this large, the 32°F shift is small enough to be neglected. The temperature in Celsius is essentially 5/9th of the reading in Fahrenheit; only 17° C dif