Part a)
As we know that energy is defined as product of power and time
so here for light bulb we know that
Power = 100 W
time = 4 hours
so energy = Power * time
[tex]E = 100 \times (4\times 3600)[/tex]
[tex]E = 1.44 \times 10^6 J[/tex]
Part b)
Now for microwave we know that
Power = 1200 W
time = 5 hours
so energy = Power * time
[tex]E = 1200 \times (5\times 3600)[/tex]
[tex]E = 2.16 \times 10^7 J[/tex]
Part C)
Light bulb is having efficiency of 1.8%
so it will convert 1.8% energy into light
Rest of the energy will be emitted into heat here
so heat energy is (100 - 1.8)% = 98.2% of total energy
so
[tex]Heat = 0.982\times 1.44 \times 10^6[/tex]
[tex]Heat = 1.41 \times 10^6 J[/tex]
Answer:
a) Energy is used by the light bulb when it is used for 4 hours:1,440,000 Joules.
b) Energy is used by the microwave when it is used for 5 minutes:360,000 Joules
c)1,414,080 Joules of heat energy will be produced by light bulb in 4 hours.
Explanation:
Power is defined as ratio of work done per unit time.
[tex]Power=\frac{Energy}{Time}[/tex]
Power of light bulb,P = 100 W
Power of microwave,P' = 1200 W
a) Energy is used by the light bulb when it is used for 4 hours:
Duration of time it is used = T = 4 hours =14,400 s
[tex]Power=\frac{Energy}{Time}[/tex]
[tex]Energy=P\times T=100 W\times 14,400 s=1,440,000 J[/tex]
b) Energy is used by the microwave when it is used for 5 min:
Duration of time it is used = T' = 5 min = 300 sec
[tex]Power=\frac{Energy}{Time}[/tex]
[tex]Energy=P'\times T'=1200 W\times 300 s=360,000 J[/tex]
c) Heat energy produced by light bulb with an efficiency of 1.8%.
Efficiency 1.8% means that light bulb gives 1.8 % of its energy into light energy remaining as heat energy.
Heat energy produced by light bulb = 100% - 1.8 % = 98.2 %
Energy used by the bulb in 4 hours = 1,440,000 J
Heat energy produced by light bulb = 98.2% of 1,440,000 J:
[tex]\frac{98.2}{100}\times 1,440,000 J=1,414,080 J[/tex]
1,414,080 Joules of heat energy will be produced by light bulb in 4 hours.
