AP Physics 2 : Electricity and Magnetism

Study concepts, example questions & explanations for AP Physics 2

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Example Questions

Example Question #2 : Understanding Dc Circuit Diagrams

Dccircuit

In the circuit diagram above, what do each of the letters represent?

Possible Answers:

A: Resistor

B: Battery

C: Solenoid

D: Capacitor

A: Battery

B: Solenoid

C: Capacitor

D: Resistor

A: Battery

B: Resistor

C: Capacitor

D: Solenoid

A: Capacitor

B: Solenoid

C: Resistor

D: Battery

A: Battery

B: Resistor

C: Solenoid

D: Capacitor

Correct answer:

A: Battery

B: Resistor

C: Capacitor

D: Solenoid

Explanation:

A represents a battery. Convention dictates that the direction of charge flow is from the small side to the large side. B is a resistor. Its symbol makes sense if you view the flow of electrons similarly to water flowing; water's flow is resisted by turns, so the jagged lines would evoke that thought for electrons flowing. C is a capacitor. Common capacitors are parallel plates of equal surface area separated by a vacuum or dielectric. This is why the lines are equal in length, unlike the battery. D is a solenoid. A solenoid is a coil of wire that induces a magnetic inside of it.

Example Question #1 : Understanding Rc Circuit Diagrams

Physics2set1q11

If  , , and the voltage source is , what is the time constant of this RC circuit?

Possible Answers:

Correct answer:

Explanation:

The time constant of this RC circuit is only dependent on the value of the resistance and the capacitor, not the voltage source.

Example Question #41 : Circuits

You have a 4cm long copper wire with a radius of 0.5mm. You have experimentally determined the resistance of the wire to be . What is the resistivity of copper?

Possible Answers:

None of the other answers is correct

Correct answer:

Explanation:

The resistivity of a material is how much the material resists the flow of charge through it. Metals have low resistivities (which makes them good conductors), while things like glass or plastic have high resistivities.

The equation for resistivity is as follows:

 is the length of the wire,  is the cross-sectional area,  is the resistance, and  is the resistivity. We have values for  and , and we're given the radius of the wire so we can find , so we're trying to solve for . If we rearrange the equation, we end up with this:

We're given the radius of the wire, so to find the area, we square the radius and multiply it by .

Now, we can plug in our values.

Therefore, the answer is .

Example Question #42 : Circuits

You create a cylinder of an unknown material that has a diameter of , and a height of . You attach the electrodes to the faces of the cylinder and find the sample has a resistance of .

What is the resistivity of the material?

Possible Answers:

Correct answer:

Explanation:

Use the equation for resistivity:

First, find the cross sectional area.

Plug in known values.

 

Example Question #43 : Circuits

You have a sample that is a cube of volume . You attach electrodes to opposite faces and find the resistance to be

What is the resistivity of the material?

Possible Answers:

Correct answer:

Explanation:

Since we have a cube of volume , the length of the material must be . Use the equation for resistivity. 

Rearrange the equation and plug in known values.

Example Question #44 : Circuits

You have a material with resistivity . You build a component of a fuel cell out of this material with a cross sectional area of  , and a thickness of .

What will be the resistance of this component?

Possible Answers:

None of these

Correct answer:

Explanation:

Use the resistivity equation:

Example Question #48 : Circuits

You are researching new materials for usage in spacecraft electronics.

You have a new material, known as "Type F."

 

You carve out a cylinder of the material. It is  tall, with a radius of .

 

You put electrodes on each face of the cylinder.

 

You determine the resistance to be .

 

What is the resistivity of "Type F?"

Possible Answers:

None of these

Correct answer:

Explanation:

We will use the relationship

 

 

 

Where  is the resistivity,  is the resistance,  is the surface area of the face the current is coming in or out of, and is the length from one face to the other.

 

Remember that the area of a circle is

 

 

Combining our equations we get

 

 

We then need to plug in our values

 

 

Example Question #862 : Ap Physics 2

You are researching new materials for usage in spacecraft electronics.

You have a new material, known as "Type G."

 

You carve out a cylinder of the material. It is  tall, with a radius of .

 

You put electrodes on each face of the cylinder.

 

You determine the resistance to be .

 

What is the resistivity of "Type G?"

Possible Answers:

None of these

Correct answer:

Explanation:

We will use the relationship

 

 

 

Where  is the resistivity,  is the resistance,  is the surface area of the face the current is coming in or out of, and is the length from one face to the other.

 

Remember that the area of a circle is

 

 

Combining our equations we get

 

 

We then need to plug in our values

 

 

Example Question #1 : Resistivity

You are researching new materials for usage in spacecraft electronics.

You have a new material, known as "Type Z."

 

You carve out a cylinder of the material. It is  tall, with a radius of .

 

You put electrodes on each face of the cylinder.

 

You determine the resistance to be .

 

What is the resistivity of "Type Z?"

Possible Answers:

None of these

Correct answer:

Explanation:

We will use the relationship

 

 

 

Where  is the resistivity,  is the resistance,  is the surface area of the face the current is coming in or out of, and is the length from one face to the other.

 

Remember that the area of a circle is

 

 

Combining our equations we get

 

 

We then need to plug in our values

 

 

 

 

Example Question #51 : Circuits

A researcher is testing the electrical properties of a circuit that contains a resistor of unknown material. The resistor is a  cylinder with a radius of . The researcher measures the resistance of the resistor to be . What is the resistivity of this unknown material? 

Possible Answers:

Correct answer:

Explanation:

Use the equation for resistivity: 

Here,  is the resistivity,  is the resistance,  is the cross-sectional area, and  is the length of the resistor.

Begin by finding the cross-sectional area of the material, which is circular: 

Now plug in all known values and solve for resistivity.

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