Chapter 10, Problem 10.51P

An electric resistance space heater is designed such that it resembles a rectangular box 55 cm high, 75 cm long, and 20 cm wide filled with 45 kg of oil. The heater is to be placed against a wall, and thus heat transfer from its back surface is negligible. The surface temperature of the heater is not to exceed 75°C in a room at 25°C for safety considerations. The emissivity of the outer surface of the heater is 0.8 and the average temperature of the ceiling and wall surfaces is the same as the room air temperature. The properties of air at 1 atm and the film temperature are: k = 0.02753 W/m-°C, v=1.798 x 10-5 m²/s, Pr = 0.7228, and ẞ= 0.003096K-1 Wall T₁ =75°C Oil € = 0.8 Electric heater Heating element Disregarding heat transfer from the bottom and top surfaces of the heater in anticipation that the top surface will be used as a shelf, determine the power rating of the heater in W. The power rating of the heater is W.

circuit 2

Suppose you have 8 LED's connected to port-B (Bo-B7) of PIC16F877A and one switch connected to port-D (Do) as shown in figure below. Write a program code that performs a nibble (4-bits) toggling: if the switch is released then LED's (Bo to B3) are OFF and LED's (B4 to B7) are ON, while if the switch is pressed then LED's (Bo to B3) are ON and LED's (B4 to B7) are OFF. Use 300ms delay for each case with 4MHz frequency. 13 14 22 NATHON 20 U1 OSC1/CLKIN U2 33 REOINT 20 34 OSC2/CLKOUT 19 RB1 35 3 18 RB2 RADIANO debt0RB3PGM 30 4 17 37 5 10 RA1/AN1 RB4 38 RA2/ANZ/VREF-/CVREF 15 RB5 39097 RA3/AN3VREF RB6/PGC 7 14 40 RA4/TOCK/C1OUT 13 RB7/PGO RAS/ANA/SS/CZOUT 15 RCO/T1OSO/TICKI 10 11 REQIANS/RD 18 RC1/T10S/CCP2 17 10 RE1/AN/WR REZ/ANTICS MCLR/Vpp/THV RC2/CCP1 LED-BARGRAPH-RED RC3/SCK/SCL RC4/SDUSDA RC5/SDO Eng of ROSTX/CX RC7/RX/DT RDO/PSPO RD1/PSP1 RD2PSP2 RO3/PSP3 RD4/PSP4 ROS/PSP5 RD6/PSP6 RD7/PSP7 PIC16F877A +5V R1 100R