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klasskru [66]
4 years ago
8

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

be combined into one light source to give a total of 1.6 W of visible-light output (comparable to the light output of a 40 W incandescent bulb)? b. What total power is necessary to run this LED light source?
Physics
1 answer:
Neporo4naja [7]4 years ago
7 0

Answer:

8, 8 W

Explanation:

The useful power of 1 Light Emitting Diode is

0.2\times 1=0.2\ W

Total power required is 1.6 W

Number of Light Emitting Diodes would be

n=\dfrac{1.6}{0.2}\\\Rightarrow n=8

The number of Light Emitting Diodes is 8.

Power would be

P=8\times 1=8\ W

The power that is required to run the Light Emitting Diodes is 8 W

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A concave mirror produces a real image that is three times as large as the object. If the object is 20 cm in front of the mirror
TiliK225 [7]

Answer:

The image is produced 60 cm behind the mirror

The focal length of the mirror is 30 cm

Explanation:

u = Object distance =  20 cm

v = Image distance

f = Focal length

m = Magnification = 3

m=-\frac{v}{u}\\\Rightarrow 3=-\frac{v}{20}\\\Rightarrow v=-3\times 20\\\Rightarrow v=-60\ cm

The image is produced 60 cm behind the mirror

\frac{1}{f}=\frac{1}{u}+\frac{1}{v}\\\Rightarrow \frac{1}{f}=\frac{1}{20}+\frac{1}{-60}\\\Rightarrow \frac{1}{f}=\frac{1}{30}\\\Rightarrow f=\frac{30}{1}=30\ cm

The focal length of the mirror is 30 cm

8 0
3 years ago
Give the SI unit. For physics
IrinaVladis [17]

Answer:

metre (m) - unit of length

kilograms (kg) - unit of mass

second (s) - unit of time

ampere (A) - unit of electrical current

kelvin (K) - unit of temperature

mole (mol) - unit of the amount of substance

Explanation:

6 0
3 years ago
. Find the buoyant force exerted on a ball with radius of 2 meters, when the ball is entirely immersed in the water.
almond37 [142]

Explanation:

Buoyancy force is equal to the weight of the displaced fluid:

B = ρVg

where ρ is the density of the fluid,

V is the volume of the displaced fluid,

and g is the acceleration due to gravity.

The fluid is water, so ρ = 1000 kg/m³.

The volume displaced is that of a sphere with radius 2 m:

V = 4/3 π r³

V = 4/3 π (2 m)³

V ≈ 33.5 m³

The buoyancy force is therefore:

B = (1000 kg/m³) (33.5 m³) (9.8 m/s²)

B ≈ 328,400 N

Round as needed.

8 0
3 years ago
Please help me with this question someone
Gekata [30.6K]
From the answers provided, I believe the possible answer would be the last option, silicon, oxygen, and one or more metals. Here's my reasoning: the most abundant mineral group found in the Earth's crust is the silicate group. The silicate materials contain both oxygen and silicon. Silicates are the most common minerals in the rock-formation process, and it has, in fact, been estimated that they make up 75 to 90 percent of the Earth's crust. From this piece of evidence, I can guess that the answer will possibly be D, silicon, oxygen, and one or more metals.
It should also be noted that the additional elements that combine with the silicon-oxygen tetrahedron are involved with the other elements commonly found in the Earth's crust and mantle. They are aluminum, calcium, iron, magnesium, potassium and sodium.
8 0
4 years ago
Read 2 more answers
A 20 N force is applied to an object causing it to move 10 m. How much work was done on the object? How much energy was needed t
olga2289 [7]

Answer:

Here, force=20N and displacement=10m

Work=Force×Displacement=20N×10m=200Nm

3 0
3 years ago
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