AP Physics 2 : AP Physics 2

Study concepts, example questions & explanations for AP Physics 2

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Example Questions

Example Question #61 : Electrostatics

Two electrons are deep in space and apart. Determine the force of one electron on the other.

Possible Answers:

None of these

Correct answer:

Explanation:

Using

Plugging in values:

Example Question #122 : Electricity And Magnetism

A mobile  charge is perfectly balanced on top of a stationary charge. What will be the equilibrium height of the mobile charge?

Possible Answers:

None of these

Correct answer:

Explanation:

Using

Combining equations and plugging in values:

Solving for

Example Question #21 : Electric Force Between Point Charges

There are two point charges suspended in space. Charge A has a charge of . Charge B has a charge of . If they are 3 meters apart, what is the magnitude of the force between them? Is the force attractive or repulsive?

Possible Answers:

; repulsive

None of these answers are correct.

; attractive

; repulsive

; attractive

Correct answer:

; attractive

Explanation:

To determine the force between two point charges, you use Coulomb's Law.

We have the values of q1, q2, and r. We already know the value of k: 9 x 109. To find the force, we can plug in each of the values.

Therefore, the magnitude of the force is 0.02. Now, to determine the direction of the force, we examine the sign. If the sign is negative, then the force is attractive. As our force value is negative, it therefore is an attractive force.

Example Question #21 : Electric Force Between Point Charges

 charge is located at the origin. A  charge is located at . Where could an electron be placed where it would experience no net force?

Possible Answers:

None of these

Correct answer:

Explanation:

Since both charges are located on the x-axis, this is a one dimensional problem.

The electron, which has a negative charge, will be repelled by both charges. 

Placing the electron somewhere "in the middle" will allow the forces to balance out.

Where

 is the constant 

 is the value of the first charge

 is the value of the second charge

 is the charge of the electron

 is the distance from the first charge to the electron

 is the distance from the second charge to the electron

 is  away from , so:

Combining equations and plugging in values:

Thus, the location of balanced forces is at:

Example Question #71 : Electrostatics

 charge is located at the origin. A  charge is located at . Where could a proton be placed where it would experience no net force?

Possible Answers:

None of these

Correct answer:

Explanation:

Since both point charges are located on the x-axis, this is a one dimensional problem.

The proton, which has a positive charge, will be repelled by both charges. 

Placing the proton somewhere "in the middle" will allow the forces to balance out.

Where

 is the value of the first charge

 is the value of the second charge

 is the charge of the proton

 is the distance from the first charge to the proton

 is the distance from the second charge to the proton

 is  away from , so:

Combining equations and plugging in values:

 

Thus, the location of balanced forces is at:

Example Question #72 : Electrostatics

An electron is  away from a point charge. It experiences a force of  towards the point charge. Determine the value of the point charge.

Possible Answers:

None of these

Correct answer:

Explanation:

Using

Solving for 

Converting  to  and plugging in values

*Note: a negative sign is used for the force because it is an attractive force, if it was a repulsive force, the opposite sign would be used.

Example Question #21 : Electric Force Between Point Charges

Which of the following will cut the magnitude of the electric force between two charged particles in half?

Possible Answers:

Reducing the charge of only one of the particles by half

Placing the two particles twice as far apart

Doubling the charge of each particle

Double the charge of only one of the particles

Reducing the charge of each particle by half

Correct answer:

Reducing the charge of only one of the particles by half

Explanation:

To answer this question, it's necessary to understand the factors that affect the electric force. To show this, we can write the electrical force expression.

Using the above expression, we can look at how each answer choice would change the electric force.

If we place the two particles twice as far apart, the magnitude of the electric force will be reduced by a factor of .

Doubling the charge of one particle would double the electric force. Doubling the charge on both particles would cause the electric force to become  times as great.

Halving the charge of both particles would cause the electric force to decrease by a factor of .

If the charge on only one of the particles is cut in half, then the electric force would be cut in half as well. Thus, this is the correct answer.

Example Question #22 : Electric Force Between Point Charges

Two charges are a fixed distance  apart. Both charges have charge . If another charge of charge  and mass  is placed a distance  from one of the charges and  from the other, what will be the magnitude of its acceleration the moment it's released?

Possible Answers:

Correct answer:

Explanation:

All we have to do is find the sum of the forces on the charge and divide by its mass. To find the force from each charge, we can use Coulomb's law:

Let's let the force from the charge a distance  away be positive. That force is . The other force will be negative because it's acting in the opposite direction. This force is . Adding these two together we get 

 

This is the magnitude of the net force. To find acceleration, we divide by the mass to get

Example Question #1 : Electric Potential Energy

 electrons pass through a  resistor in 11 minutes. What is the potential difference across that resistor?

Possible Answers:

Correct answer:

Explanation:

We need to find the voltage, and we have the resistance, so if we can find the current, then we can use Ohm's Law to find the voltage.

The definition of current is amount of charge that flows through a point in  time, so current can be calculated using this equation:

We're told how many electrons have passed through a resistor, and we know how much charge a single electron has. If we convert the number of electrons into total amount of charge, we can divide that number by the amount of time in seconds to find the current.

Now we have the amount of charge in  and the amount of time in seconds, so we divide the two.

Now that we have the current, we can use Ohm's Law to find the voltage.

Therefore, the potential difference is 2.96V.

Example Question #1 : Electric Potential Energy

What is the electric potential between two terminals of a cell if it requires  of work to transfer  between the terminals?

Possible Answers:

Correct answer:

Explanation:

Write the formula for the potential difference.

Substitute the work and charge. The unit is in volts.

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