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

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Hold down the T key for 3 seconds to activate the audio accessibility mode, at which point you can click the K key to pause and resume audio. Useful for the Check Your Understanding and See Answers.

 The Question

What is the resistance (in ohms) of an appliance that has a power rating of 89 Watts when connected to a 120-Volt outlet? (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 equation above can be used to solve for the resistance of an appliance from knowledge of the power (in Watts) and the electric potential difference (in Volts). The equation above 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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