4.2.2 Electrical Resistance

4.2.2 Electrical Resistance

by David Bittinger

​•resistance: OPPOSITION TO CURRENT

•unit: Ohm (Ω)

​

•factors that change resistance:

​ •resistivity: MATERIAL  

•length

•cross-sectional area

•temperature

​Jump to slide 3 &4 of ppt.

​Hallway analogy

Multiple Choice

Which material has the lowest resistivity?

• Gold

• Tungsten

• Nichrome

• Aluminum

Multiple Choice

Which material is the best conductor of electricity?

• Gold

• Tungsten

• Nichrome

• Aluminum

Multiple Choice

Determine the resistance of a 1.0 meter long copper wire with a cross-sectional area of 0.01 m^2

• 10,000 $$\Omega$$  

• 100 $$\Omega$$  

• 1.72E-4 $$\Omega$$  

• 1.72E-6 $$\Omega$$  

Multiple Choice

A piece of wire that has a length of 5.0E7 meters and a cross-sectional area of 0.025 m^2 has a resistance of 31.8 ohms

• 1.59E-8 $$\Omega m$$  

• 3.975E-10 $$\Omega m$$  

• 0.159 $$\Omega m$$  

• 0.0199 $$\Omega m$$  

Multiple Choice

Which change decreases the resistance of a piece of copper wire?

• Increasing the wire's length

• Increasing the wire's resistivity

• Decreasing the wires temperature

• Decreasing the wire's diameter

Multiple Choice

What is the resistance of a 20.0 meter long tungsten rod with a cross-sectional area of 1.00E-4 m^2 at 20 degrees Celsius?

• 2.80E-5 $$\Omega$$  

• 1.12E-2 $$\Omega$$  

• 89.3 $$\Omega$$  

• 112 $$\Omega$$  

Multiple Choice

The diagrams represent four pieces of copper wire ate 20 degrees Celsius. For each piece of wire, l represents a unit of length and A represents a unit of cross-sectional area. The piece of wire that has the greatest resistance is

• wire 1

• wire 2

• wire 3

• wire 4