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Home Minds On Electric Circuits Mission EC6 P, V, I, R, and Cost Calculations Help Help 1

Mission EC6 P, V, I, R, and Cost Calculations

The Question

What is the resistance (in ohms) of a typical 40-Watt light bulb plugged into a 120-Volt outlet in your home? (Enter your answers to the second decimal place.)
 
(Note: The numbers in this problem are randomly selected and may differ from those above.)

Formula Fix

The power (P) or rate at which energy is transformed by a light bulb is related to the electric potential difference (or voltage drop or ∆V) impressed across it and the resistance (R) of it. These quantities are related by the equation
 
P = ∆V2/ R.

Math Magic

The Power equation can be used to solve for the resistance of a light bulb from knowledge of the power (in Watts) and the electric potential difference (in Volts). The equation is set up to solve for power. You will need to rearrange the equation to get the variable R by itself. Take your time and use appropriate algebra skills.

Bright Idea

This mission focuses on numerous electrical quantities and their relationship with one another. Having a solid grasp of the quantities will be crucial to your success on this mission. It would be a wise idea to develop a list of such quantities, the units used to express them, the symbol used to represent them and the equations that relate them. The quantities that you might want to have on your list include power, energy, resistance, current, voltage and cost.

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