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.
Answer:
<em>Rt = 8 ohm</em>
<em>I = 2 A</em>
<em>Vab = 12 V</em>
<em>VbΓ = 4 V</em>
<em>VaΓ = 16 V</em>
Explanation:
<u>Electric Circuits</u>
We'll apply Ohm's formula to solve the circuit shown on the image:
V = R.I
Where V is the voltage, R is the resistance, and I is the current.
The circuit has two resistances connected in series, thus the total resistance is:
Rt = R1 + R2 = 6 ohm + 2 ohm = 8 ohm
Now the current is:
I = 2 A
The voltages are calculated below:
Vab = R1 * I = 6 ohm * 2 A = 12 V
VbΓ = R2 * I = 2 ohm * 2 A = 4 V
VaΓ = Vab + VbΓ = 12 V + 4 V = 16 V
Answer:
0.33 mV or 0.00033 V
Explanation:
Parameters given:
Radius, r = 4 cm = 0.04 m
Number of turns, N = 1
Initial magnetic field, Bini = 0.069 T
Final magnetic field, Bfin = 0.043 T
Time, t = 0.4 secs
EMF induced in a coil is given as the time rate of change of Magnetic Flux:
EMF = -ΔΦ/t
ΔΦ = ΔB * A
Where ΔB = change in magnetic field
A = area = pi * r²
EMF = -[(Bfin - Bini) * N * pi * r²] / t
EMF = -[(0.043 - 0.069) * 1 * 3.142 * 0.04²] / 0.4
EMF = 0.00033 V = 0.33 mV
<span>1) check your tools for chips or breaks before beginning your experiment.
2) keep your work surface neat and clean
3) read and follow safety instructions and the materials you will need to use in the investigation. </span>
Answer:
The time taken to stop the box equals 1.33 seconds.
Explanation:
Since frictional force always acts opposite to the motion of the box we can find the acceleration that the force produces using newton's second law of motion as shown below:
Given mass of box = 5.0 kg
Frictional force = 30 N
thus
Now to find the time that the box requires to stop can be calculated by first equation of kinematics
The box will stop when it's final velocity becomes zero
Here acceleration is taken as negative since it opposes the motion of the box since frictional force always opposes motion.