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Ohm's Law
In many materials, the voltage and resistance are connected by Ohm's Law:
Ohm's Law : V = IR
The connection between voltage and resistance can be more complicated in some
materials.These materials are called nonohmic. We'll focus mainly on ohmic
materials for now, those obeying Ohm's Law.
Example
A copper wire has a length of 160 m and a diameter of 1.00 mm. If the wire is
connected to a 1.5volt battery, how much current flows through the wire?
The current can be found from Ohm's Law, V = IR. The V is the battery voltage, so if
R can be determined then the current can be calculated. The first step, then, is to find
the resistance of the wire:
L is the length, 1.60 m. The resistivity can be found from the table on page 535 in the
textbook.
The area is the crosssectional area of the wire. This can be calculated using:
The resistance of the wire is then:
The current can now be found from Ohm's Law:
I = V / R = 1.5 / 3.5 = 0.428 A
Electric power
Power is the rate at which work is done. It has units of Watts. 1 W = 1 J/s
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This note was uploaded on 11/22/2011 for the course PHY PHY2053 taught by Professor Davidjudd during the Fall '10 term at Broward College.
 Fall '10
 DavidJudd
 Physics, Resistance

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