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# The Physicics behind An Electric Pencil Sharpener

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## Brianna Yusiewicz

on 16 April 2014

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#### Transcript of The Physicics behind An Electric Pencil Sharpener

The Physics behind an Electric Pencil Sharpener
The Physics behind An Electric Pencil Sharpener
The Voltage Source
After being plugged into an electrical outlet, current runs through the wires inside the plug. The pencil sharpener uses 120 Volts, and has a current of 2 Amps. Knowing this, we can find that the resistance in this circuit is 60 Olms.

Knowns
V = 120V R = V/I = 60 Olms
I = 2A
R = ?
Bibliography
The Motor
Completing the Circuit
Upon pushing a pencil into a pencil sharpener, pressure is applied to a button inside. Pressing this button completes the circuit and allows the motor and other workings inside of the sharpener to begin moving.
2.jpg

How it Works
The motor contains a permanent magnet and an electromagnet shaft which is spun inside the field of the permanent magnet by repeatedly changing the polarity on the magnet.
Once the shaft makes a half-turn from the original position the polarity of the magnet flips forcing the other half of the blades to turn.

A pencil is placed inside the entrance sharpener where there is a sharp metal blade tilted at a special angle. This angle will give the pencil its pointy shape. The blade then shaves off the wood and graphite of the pencil until the pencil is ready to write!

Evans, Keith. "How Does a Pencil Sharpener Work?" EHow. Demand Media, 28 Oct. 2008. Web. 31 Mar. 2014.
Hira, Maggie. "What Simple Machines Are in a Pencil Sharpener?" EHow. Demand Media, 12 Nov. 2008. Web. 31 Mar. 2014.
"Physicseducation." Pearltrees. N.p., n.d. Web. 30 Mar. 2014.
Radder, Jan. "Types of Simple Machines in a Pencil Sharpener." EHow. Demand Media, 08 Mar. 2011. Web. 31 Mar. 2014.
The type of motor in a pencil sharpener is a single phase motor.
Rods and chains

--> carry current to gears in motor
Gears
--> transfer electrical energy to razor, causing it to spin and sharpen the pencil
Cam
-->small wheel on a shaft that causes the motor to oscillate
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