Answer a) roof equilibrium temperature is 400K
Explanation:
The roof surface is sorrounded by ambient air whose temperature is 300K and which has a convective coefficient h of 10W/m2-K.
This means that heat will be conducted to the roof from the air around at an heat Flux of 300K x 10W/m2-K = 3000w/m2
For a clear solar day with solar heat Flux of 500W/m2, total heat Flux on roof will be
Q = 500 + 3500 = 3500W/m2
Q = h(Tr-Ta)
Ts is temperature of roof,
Ta is temperature of air
3500 = 10(Tr - 50)
350 = Tr - 50
Tr = 400k
Answer b): roof equilibrium temperature will be 350K
Explanation:
At night total heat Flux is only due to hot ambient air sorrounding the surface of the roof.
Q = 3000W/m2
Q = h(Tr-Ta)
3000 = 10(Tr-50)
300 = Tr - 50
Tr = 350K
Answer:
It is a perpetual motion machine.
Explanation:
The claim of an inventor is not valid because a device can not deliver more energy than it input or there is no device that can produce more energy than it input. Therefore, the compressor cannot produce more energy as compared to another conventional heating system that runs by the e power input. However, the claim of inventor violates the rule or first law of thermodynamics and So, it is only a perpetual motion of first kind PMM1.
Answer:
Diameter will be 27394.76 m
Explanation:
Power P = 0.5 kW = 500 W
Time t required for grinding = 1 hr = 3600 sec
Energy required E = P x t
E = 500 x 3600 = 1800000 J
Flow rate of water Q = 400 ltr/min
We convert to m3/sec
400 ltr/min = 400/(1000 x 60) m3/ses
Q = 0.0067 m3/sec
Energy provided by flow will be
E = pgQd
Where p = density of water = 1000 kg/m3
g = acceleration due to gravity 9.81 m/s2
d = diameter of wheel.
Equating both energy, we have,
1800000 = 1000 x 9.81 x 0.0067 x d
1800000 = 65.73d
d = 1800000/65.73
d = 27394.76 m
Answer:
a) λ = 2 meters
b) λ = 1.76 meters
c)In free space: length of phasing section = 0.5 meters and in dielectric medium: length of phasing section =0.44 meter
Explanation:
Given that:
velocity factor = 0.88
operating frequency = 150 MHz = 150 × 10⁶ Hz
phasing section is a quarter-wavelength = λ/4
a) Wavelength of free space:
λ = c/f
where c is the speed of light = 3×10⁸
λ = (3×10⁸)/150 × 10⁶
λ = 2 meters.
b) Wavelength of dielectric:
Velocity of dielectric = speed of light (c) × velocity factor
Velocity of dielectric = 3×10⁸ × 0.88 = 2.64 × 10⁸ m/s
wavelength dielectric = Velocity of dielectric /f = (2.64 × 10⁸)/150 × 10⁶ =1.76
wavelength dielectric = 1.76 meters
c) length of the phasing section in meters:
l = λ/4
In free space:
l = 2/4 = 0.5 meter
In dielectric
l = 1.76/4 = 0.44 meter
Answer:a is the answer i’m pretty sure yea i think it is