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AnnZ [28]
3 years ago
5

How many LEDs must be combined into one light source to give a total of 3.8 W of visible-light output (comparable to the light o

utput of a 100 W incandescent bulb)?
Physics
1 answer:
notka56 [123]3 years ago
4 0

Answer:

This is an incomplete question. The complete question is --

An individual white LED (light-emitting diode) has an efficiency of 20% and uses 1.0 W of electric power.

How many LEDs must be combined into one light source to give a total of 3.8W of visible-light output (comparable to the light output of a 100W incandescent bulb)?

And the answer is --

19 LEDs

Explanation:

The full form of LED is Light emitting diode.

It is given that the efficiency of the LED bulb is 20 %

1 LED uses power = 1 W

So the output power of 1 LED = 0.2 W

We need to find the power required to give a 3.8 W light.

Power required for 3.8 W = Number of LEDs required  =   (total required power  /  power required for 1 LED )

                                                                                         = 3.8 / 0.2

                                                                                         = 19

Therefore, the number of LEDs required is 19.

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A NATO base in northern Norway is warmed with a heat pump that uses 7.0 °C ocean water as the cold reservoir. Heat extracted fro
tatiyna

Answer:

3.33, 4.84

Explanation:

A) Actual coefficient of performance can be calculated by the formula stated below

Actual COP = heat delivered/ work required

Actual COP = 2,000/600

Actual COP = 3.33

B) Th = High temperature = 80°C + 273 = 353K

Tl = Low temperature = 7°C + 273 = 280K

The theoretical maximum coefficient of performance can ve calculated by the formula

Theoretical COP = Th/(Th-Tl)

Theoretical COP = 353/(353-280)

Theoretical COP = 353/73

Theoretical COP = 4.84

3 0
4 years ago
A person weighing 0.9 kN rides in an elevator that has a downward acceleration of 1.9 m/s^2. The acceleration of gravity is 9.8
Keith_Richards [23]

Answer:

The magnitude of the force is 0.7255kN

Explanation:

The elevator floor acts on the person with a force that is due to the gravitational acceleration less the downward acceleration of the elevator:

(force of floor F) = (mass of person m) x [ (grav. acceleration g) - (elevator acceleration a) ]

in other words, considering the elevator floor as a reference frame in the Earth's gravitational field, the person's weight decreases due to the downward acceleration, as follows:

F = m\cdot(g-a)

We are given the person's weight at rest, 0.9kN, from which the mass can be determined as:

900 N = m\cdot g \implies m = \frac{900N}{9.8 \frac{m}{s^2}}

So

F = \frac{900N}{9.8 \frac{m}{s^2}}\cdot(9.8-1.9)\frac{m}{s^2}\approx 725.5N=0.7255kN

3 0
3 years ago
Why was the idea of plate tectonics difficult for many scientists to accept for many years after it was first introduced?
pentagon [3]
I think the correct answer from the choices listed above is the second option. The <span> idea of plate tectonics was difficult for many scientists to accept for many years after it was first introduced because there </span><span>was no explanation yet for how it was happening. It was only to the recent times that these were proven. </span>
3 0
3 years ago
Which of the following are scalar quantities?
kirill [66]

Speed, being a scalar quantity, is the rate at which an object covers distance. The average speed is the distance (a scalar quantity) per time ratio. ... Velocity is the rate at which the position changes. The average velocity is the displacement or position change (a vector quantity) per time ratio.

3 0
3 years ago
Sheila uses a 45N force on her bowling ball across a 15m lane. What work did she do on the bowling ball? Show your work.​
Maurinko [17]

Answer:

675J

Explanation:

Given parameters:

Force  = 45N

Distance  = 15m

Unknown:

Work done by Sheila  = ?

Solution:

Work done by a body is the amount of force applied to make a body move through a distance;

         Work done  = Force x distance

 Now;

          Work done  = 45 x 15  = 675J

6 0
3 years ago
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