The power rating on a light bulb indicates how much power it would dissipate whe

Question

The power rating on a light bulb indicates how much power it would dissipate when it is hooked up to the standard household voltage of 120 V (this rating does not mean that the light bulb always dissipates the same amount of power, assume that the resistance is constant in this case).

A. How much power is dissipated in a light bulb that is normally rated at 75 W, if instead we hook it up to a potential difference of 60 V?

B. How much power is dissipated in a light bulb that is normally rated at 75 W, if instead we hook it up to a potential difference of 120 V?

Explanation / Answer

A)

P = rated power = 75 watt

V= rated voltage = 120 Volts

R = rated resistance = V2/P = (120)2/75 = 192 ohm

V' = Voltage applied = 60 Volts

P' = actual power dissipated = V'2/R = 602/192 = 18.75 Watt

B)

P = rated power = 75 watt

V= rated voltage = 120 Volts

R = rated resistance = V2/P = (120)2/75 = 192 ohm

V' = Voltage applied = 120 Volts

P' = actual power dissipated = V'2/R = 1202/192 = 75 Watt

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.