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QveST [7]
3 years ago
14

A lightbulb has a power of 100 W and is used for 4 hours. A microwave has a power of 1200 W and is used for 5 minutes. How much

energy is used by the lightbulb? How much energy is used by the microwave? The lightbulb has an efficiency of 1.8%. How much heat energy does the lightbulb produce in 4 hours?
Physics
1 answer:
ladessa [460]3 years ago
4 0

Answer:

a. E=1440KJ

b. E=360KJ

c. E=1.8 J

Explanation:

I have the power (Watts) is expressed as Energy (Joules) / Time (seconds), also I have to1hour * \frac{60min}{1hour}*\frac{60s}{1min}\\1h=3600s

so, for the lightbulb

100W= \frac{Energy}{3600s*4}\\Energy=100W*14400s\\ E=1440000J =1440KJ

Analogously, for the microwave

1200W= \frac{Energy}{60s*5}\\Energy=1200W*300s\\ E=360000J =360KJ

Now, I have to express the efficiency as Heat energy / power * 100 so1.8= \frac{Heat Energy}{100W}*100\\Heat Energy=1.8J

Done

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\frac{N_P}{N_s} = \frac{E_p}{E_s} \\\\E_s = \frac{N_sE_p}{N_p} \\\\E_s = \frac{1875*130}{375} \\\\E_s = 650 \ V

The rms voltage (in V) measured across the secondary coil is calculated as;

V_{rms} = \frac{V_0}{\sqrt{2} } = \frac{E_s}{\sqrt{2} } \\\\V_{rms} = \frac{650}{\sqrt{2} } = 459.62 \ V

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