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Transformers are designed as a step-up or step-down working on the principle of self-induction an auto transformer can act as either a step-up or step-down and works on the principle of mutual induction.

If a transformer has an input power of 400 watts and an output power of 200 watts what is the efficiency?

There are 4 types of mA selectors.

1D) (5 points) In a plane wall, there is internal heat generation  and the wall is thermally insulated on its left side. The right side of the wall is cooled by forced convection with a fluid temperature of 20 ℃ and a convection coefficient of 500 W/m2K. If wall’s thickness is 30 mm, what would be the wall’s temperature on its right surface (Ts)?

1B) (5 points) Consider a room whose air temperature is maintained at 23ºC, while the walls of the room are nominally at 25°C. The exposed surface of a person in the room may be assumed to be at a temperature of 32°C and to have an emissivity of 0.91. Stefan-Boltzmann constant is 5.67´10-8 W/m2K4. Calculate the following.  Heat flux due to radiation from a person to surrounding wall.

Problem 3. (40 points) An air-cooled heat sink with 9 plate fins is used to maintain a CPU at 80°C. There is contact resistance of  between the CPU and the base of the sink. Thermal conductivity of the heat sink is 160 W/(m×K). Geometric variables are as follow: fin thickness (tf) = 2 mm, fin length (Lf) = 12 mm, cross-sectional shape of CPU = 2 cm x 2 cm (square), heat sink’s base thickness (tb) = 3 mm. Air temperature is 25°C and convection coefficient is 50 W/(m2K). Ignore internal heat generation and radiation heat transfer. Assume that the fin tips are adiabatic. Draw a thermal resistance circuit that expresses the heat transfer from the CPU’s top surface to air. Below the circuit show the expressions for thermal resistances (e.g., expression for a radiation resistance is 1/hrA). Then, determine the 1) total resistance in K/W (or °C/W) 2) overall fin efficiency and 3) heat rate from CPU to air in W.

What will be the output of the following code snippet? If the program results in an error, put down ‘ERROR’.  x = 0y = 8while x < y:    y -= 1    x = int(y/2)    if x % 2 != 0:        x += 1print(x)

Which of the following is true about metabolic bone disease?

What does this function return if it is called as min_value(1131, 1311)?  If the program results in an error, put down ‘ERROR’. def min_value(x, y):     return x if x < y else y

What will be the output of the following code snippet? If the program results in an error, put down ‘ERROR’.  x = 0for i in range(5):    while i > 0:        x += i        i -= 2print(x)