All AP Physics 2 Resources
Example Questions
Example Question #61 : Circuits
A cylindrical resistor is long with a diameter of . Determine the resistivity of the material if the resistance is .
Use the following relationship:
Where is the resistivity
is the resistance
is the length
is the cross sectional area
Convert and to and plug in values:
Example Question #222 : Electricity And Magnetism
Suppose that the resistance of an unknown conductive material is found to be . Considering that the cross-sectional area of this material is and its length is , what is the resistivity of this unknown material?
In this question, we're presented with the length and area of a given material, as well as the resistance of the material. We're being asked to find the resistivity of this material.
First, it's important to distinguish between resistance and resistivity. Resistance represents the impediment to the flow of charge that is caused by such factors as the length and cross-sectional area of the material. Resistivity is a value that is intrinsic to each material; changing the cross-sectional area or the length will not affect the resistivity.
To solve this problem, we'll need to utilize the equation that relates resistance and resistivity:
From this equation, we can see that as the length of the conductive material increases, so too does the resistance of that material. However, as the area increases, the resistance decreases.
We can go ahead and rearrange this equation in order to isolate the resistivity term, .
Next, we can plug in the values that we have in order to solve for our answer:
Example Question #62 : Circuit Properties
A single resistor of radius and length is placed into a circuit with a single voltage source of . If the current is , determine the resistivity of the resistor.
None of these
Using
and
Combining equations:
Solving for :
Converting and to and plugging in values:
Example Question #63 : Circuit Properties
A resistor has cross sectional area and length . When placed in series with a battery, a current of is produced. Determine the resistivity.
None of these
Using Ohm's law:
Converting to and plugging in values
Solving for resistance:
Using the equation for resistivity:
Converting to and to and plugging in values:
Example Question #64 : Circuit Properties
A resistor has cross sectional area and length . When placed in series with a battery, a current of is produced. Determine the resistivity.
None of the above
Using Ohm's law:
Converting to and plugging in values
Solving for resistance:
Using the equation for resistivity:
Converting to and to and plugging in values:
Example Question #65 : Circuit Properties
A resistor is made out of a material. The resistor has a cross-sectional area of and a length of . It is found to have a resistance of . A new resistor is built that has a length of and a cross sectional area of . Determine the resistance of the new resistor.
None of these
Using
Plugging in values
Using
Plugging in values
Example Question #66 : Circuit Properties
identical resistors are placed in parallel. They are placed in a circuit with a battery. If the current through the battery is , determine the resistivity of each resistor. Each resistor is long and has a diameter of .
None of these
Since each resistor is in parallel, the voltage drop across each will be .
Since each resistor is identical, they all have the same resistance.
Using
and
It is determined that
Using
for all three resistors
Using definition of resistivity:
Example Question #21 : Resistivity
A resistor is made out of a material. The resistor has a cross-sectional area of and a length of . It is found to have a resistance of . Determine the resistivity of the material.
None of these
Use the equation for resistivity:
Plugging in values
Example Question #68 : Circuit Properties
A resistor is made out of a material. The resistor has a cross-sectional area of and a length of . It is found to have a resistance of . A new resistor is built that has a length of and a cross sectional area of . Determine the resistance of the new resistor.
None of these
Use the equation for resistivity:
Plugging in values
Using
Plugging in values
Example Question #231 : Electricity And Magnetism
A resistor is made out of a material. The resistor has a cross-sectional area of and a length of . It is found to have a resistance of . A new resistor is built that has a length of and a cross sectional area of . The new resistor is placed in series with a battery. Determine the current through the resistor.
None of these
Use the equation for resistivity:
Plugging in values
Rearrange the same equation and solve for resistance:
Plugging in values
Use Ohm's law to find current: