physics

posted by .

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 by 13 % to 104 V.(Caution: The 1200- W label is valid only when 120 V is applied. When the voltage is lowered, it is the resistance of the toaster, not its power, that remains constant.)
1)By how much does the current decrease?
2)By how much does the power decrease?

  • physics -

    R = 120V / 10A = 12 Ohms.

    1. I = V/R = 104 / 12 = 8.67 Amps.
    Change = 10 - 8.67 = 1.33 Amps.

    2. P = VI = 104 * 8.67 = 902 Watts.
    Change = 1200 - 902 = 298 Watts.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Circuts

    A wye-connected load consists of three impedances of 12+j3 ohms each. The line voltage driving the load is 208V. What is the phase voltage?
  2. physics

    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 …
  3. 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 …
  4. Physics

    Suppose there are two transformers between your house and the high-voltage transmission line that distributes the power. In addition, assume your house is the only one using electric power. At a substation the primary of a step-down …
  5. physics

    when the voltage across a resistor is v the power delivered is p. if the voltage if doubled to 2v, the power delieverd becomes
  6. physics

    The function of those little black transformers that clog your power strips is to step down line voltage to run small electronic gadgets. Suppose a fax machine uses an ideal transformer with a primary voltage of 120 V and primary windings. …
  7. 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 …
  8. phsyics

    A light bulb rated by the manufacturer as using and average power of 128.0 W when connected to a 73.0 Hz power source having a maximum voltage of Vmax = 189 V (the effective voltage under these conditions is what is called RMS voltage …
  9. Transformers

    Two 6600/ 250 V transformers have the following short circuited characteristics: Applied voltage 200 V, current 30 A, power input 1200 W for one of the transformers; the corresponding data for other transformer being 120 V, 20 A and …
  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