About 2% of the energy used by an incandescent light bulb is emitted as visible

Question

About 2% of the energy used by an incandescent light bulb is emitted as visible light. About 15% of the energy used by a compact fluorescent bulb is emitted as visible light. The wattage rating a blub gives the total power consumed. Which emits more visible power? A 100 W light incandescent light bulb or a 32 W compact fluorescent light bulb? What is the resistance of a 100 W light bulb. (Assume that the voltage across the bulb is 120 V.) What is the resistance of a 32 W light bulb. (Assume that the voltage across the bulb is 120 V.) What is the current through a 100 W light bulb. (Assume that the voltage across the bulb is 120 V.) What is the current through a 32 W light bulb. (Assume that the voltage across the bulb is 120 V.)

Explanation / Answer

A) incandescent ligt emits 2% energy as visible light

hence visible emitted light power = 100 x 2 /100 = 2 W

Compact fluroscent ligt emits 15% energy as visible light

hence visible emitted light power = 32x 15 /100 = 4.8 W

hence Compact fluroscent emitts more visible power.

B) P = V^2 /R

100 = 120^2 / R

R = 144 ohm

C) 32 = 120^2 / R

R = 450 ohm

D) P = VI

100 = 120 I

I = 0.83 A

E) P = VI

32 = 120 I

I = 0.27 A

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