a. cool air warms as it mixes with denser air
Explanation:
c. warm air is displaced by cooler denser air
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Answer:
a. 960 W b. One 1 kW room heater
Explanation:
a. The rate of heat conduction P = kA(T₂ - T₁)/d where k = 2 × 0.040 W/m-K = 0.080 W/m-K since the thermal conductivity of glass wool is 0.040 W/m-K and that of the material is twice the thermal conductivity of glass wool, A = area of walls = 120 m², T₁ = outside surface temperature = 5.0 °C, T₂ = inside surface temperature = 18.0 °C and d = thickness of wall = 13.0 cm = 0.13 m
P = kA(T₂ - T₁)/d
= 0.080 W/m-K × 120 m²(18.0 °C - 5.0 °C)/0.13 m
= 9.6 Wm/K × 13 K/0.13 m
= 124.8 Wm/0.13 m
= 960 W
b. The number of 1 kW room heater required will be
n = rate of heat conduction/power of one room heater = 960 W/ 1 kW = 960 W/1000 W = 0.96 ≅ 1
So we need only one 1 kW room heater.
Answer:
Turns of the primary coil: 500
Current in the primary coil: Ip= 0.01168A
Explanation:
Considering an ideal transformer I can propose the following equations:
Vp×Ip=Vs×Is
Vp= primary voltaje
Ip= primary current
Vs= secondary voltaje
Is= secondary current
Np×Vs=Ns×Vp
Np= turns of primary coil
Ns= turns of secondary coil
From these equations I can clear the number of turns of the primary coil:
Np= (Ns×Vp)/Vp = (20×120V)/4.8V = 500 turns
To determine the current in the secondary coil I use the following equation:
Is= (1.4W)/4.8V = 0.292A
Therefore I can determine the current in the primary coil with the following equation:
Ip= (Vs×Is)/Vp = (4.8V×0.292A)/120V = 0.01168A
It passes through C the Electron Cloud
