If it produces 20J of light energy in a second, then that 20J is the 10% of the supply that becomes useful output.
20 J/s = 10% of Supply
20 J/s = (0.1) x (Supply)
Divide each side by 0.1:
Supply = (20 J/s) / (0.1)
<em>Supply = 200 J/s </em>(200 watts)
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Here's something to think about: What could you do to make the lamp more efficient ? Answer: Use it for a heater !
If you use it for a heater, then the HEAT is the 'useful' part, and the light is the part that you really don't care about. Suddenly ... bada-boom ... the lamp is 90% efficient !
Choices A, B, and D are false statements.
I think choice-C is trying to say the right thing, but it
might have gotten copied incorrectly.
Electric fields and electric forces both increase as the distance
decreases, and decrease as the distance increases.
a)
for the puck :
F = force applied in the direction of pull
N = normal force on the puck in upward direction by the surface of table
W = weight of the puck in down direction due to force of gravity
b)
along the vertical direction , normal force balance the weight of the puck , hence the net force is same as the force of pull F .
so F = ma where m = mass of puck , a = acceleration
Fnet = F
c)
since the net force acts in the direction of force of pull F , hence the puck accelerates in the same direction .
Decelerate
<u>Explanation:</u>
If a charged object is moving against an electric force, the electric force would cause the charged object to decelerate. Rate of deceleration would depend on the amount of the charge the object posses and amount of the opposing electric force.
This could be understood by visualising a hypothetical situation where a charged object is moving against an electric force. Since the object is charged, it would exert a force in its direction of motion which would be opposed by the electric force, thus causing it to decelerate
Answer:
(a) Initial volume will be 7.62 L
(b) Final temperature will be 303.85 K
Explanation:
We have given one mole of ideal gas done 3000 J
So work done W = 3000 J
Let initial volume is 
and initial pressure 
( As pressure is constant )
Final volume 
= 0.025 
Number of moles n = 1
(B) From ideal gas of equation we know that 
So 
T = 303.85 Kelvin
(B) For isothermal process work done is equal to
So initial volume will be 7.62 L
