Electric Circuits Legacy Problem #6 Guided Solution
Problem*
A power saw at the local hardware store boasts of having a 15-Amp motor. Determine its resistance when plugged into a 110-Volt outlet.
Audio Guided Solution
One of the most common equations in electric circuitry is the equation that voltage is equal to current multiplied by resistance, or in equation form, that's V equals I times R. Here we're given the voltage of an electrical outlet into which a power saw is plugged into and it's said to have a 15 amp motor. So as you read through this you're going to have to recognize that when you see something in amps that you know that that is a current. So what we have is V equals 110 volts and I equals 15 amps, and if we plug those two numerical values into the equation, V equals I times R, we'll be able to solve for resistance. Now when you do, you would get resistance in units of volts per amps, which is identical to the unit ohms. And so you would end up with 7.3333 ohms, and you can round that to two significant digits, 7.3 ohms.
Solution
7.3 Ω
Habbits of an Effective Problem Solver
- Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
- Identify the known and unknown quantities and record them in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., \(\descriptive{\text{δV}}{δV,change in voltage} = 9.0\unit{\volt}\); \(\descriptive{R}{R,resistance} = 0.025\unit{\ohm}\); \(\descriptive{I}{I,current} = \colorbox{gray}{Unknown}\).
- Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
- Identify the appropriate formula(s) to use.
- Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.
Read About It!
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