physics

posted by .

During a “brownout,” which occurs when the power companies cannot
keep up with high demand, the voltage of the household circuits drops below its normal 120 V. (a) If
the voltage drops to 108 V, what would be the power consumed by a “100 W” lightbulb (that is, a
lightbulb that consumes 100.0 W when connected to 120 V)? Ignore (for now) changes in the
resistance of the lightbulb filament. (You can ignore the fact that household voltage is AC and treat
the problem as if it was normally 120 V DC.) (b) More realistically, the lightbulb filament will not be
as hot as usual during the brownout. Does this make the power drop more or less than what you
calculated in part (a)? Explain your answer by doing a calculation or algebra to show which way it
changes.

I have calculated my current as P=IV, when P=100W and V=100V, so I=0.833, and from there, I multipled I=0.88 and V=108 to get P=90W.

I know that when a filament is not as hot, the light will not be as bright, so that means less power, right? I'm confused about the last part of the question, what exactly are they asking? They want to know how the power changes, so would I just do P1=V1I1> P2=V2I2? to show that the power is less when the voltage is less?

Thanks for any help. I hope I'm at least on the right track!

  • physics -

    I think that power is actually equal to the change in voltage multiplied by the current, not just the voltage itself. Or at least that is what my formula sheet says. Good luck! I'm working on the same question

  • physics -

    I think the delta in front of voltage is just there because measured voltage is the potential difference, ie. delta

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. ap physics

    can you please check my answers and help me with one question?
  2. Physics help please!

    Hi all. I posted earlier but I'm still stuck on part of this problem. I thought that statements 2 and 3 were correct below. But I got the problem wrong. Any help would be great! Can the voltage across any of the three components in …
  3. Physics circuit help please!

    Hi all. I posted earlier but I'm still stuck on part of this problem. I thought that statements 2 and 3 were correct below. But I got the problem wrong. Any help would be great! Can the voltage across any of the three components in …
  4. physics

    for circuits with either an inductor or capacitor, the current gets out of phase with the voltage. for these circuits how are the frequencies of the current and voltage related?
  5. physics

    In periods of peak demand, power companies lower their voltage. This saves them power (and saves you money!). To see the effect, consider a 1200- W coffeemaker that draws 10 A when connected to 120 V. Suppose the voltage is lowered …
  6. physics

    In periods of peak demand, power companies lower their voltage. This saves them power (and saves you money!). To see the effect, consider a 1200- W coffeemaker that draws 10 A when connected to 120 V. Suppose the voltage is lowered …
  7. Physics

    During a brown-out, the electric power company drops the voltage of the power line and the incandescent light bulbs in your house become dimmer. When this happens, the filaments in the bulbs operate at a lower than normal temperature, …
  8. science

    A linear circuit is shown below in Figure 1. Figure 1 The elements in this circuit have the following values: R1=100Ω, R2=200Ω, R3=350Ω, V=5V, and I=0.004A. Determine the potentials drops vA and vB across resistors R1 …
  9. Physics

    A neighbourhood requires 1.5 x 10^5 w of electricity to power all homes during peak usage times. A step-down transformer is used on the high voltage transmission lines to lower the voltage to 120v for household use. There are 25000 …
  10. help

    If you know the power rating of an appliance and the voltage of the line it is attached to, you can calculate the current the appliance uses by A. multiplying the voltage by the power. B. subtracting the power from the voltage. C. …

More Similar Questions