AP Physics 2 : Electricity and Magnetism

Study concepts, example questions & explanations for AP Physics 2

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Example Questions

Example Question #1 : Circuit Power

Combined circuit

In the circuit above, find the power being dissipated by .

Possible Answers:

None of these

Correct answer:

Explanation:

First, find the total resistance of the circuit.

 and  are in parallel, so we find their equivalent resistance by using the following formula:

Next, add the series resistors together.

Use Ohm's law to find the current in the system.

The current through  and  needs to add up to the total current, since they are in parallel.

Also, the voltage drop across them need to be equal, since they are in parallel.

Set up a system of equations.

Solve.

The equation for power is as follows:

 

 

Example Question #2 : Circuit Power

Three parallel resistors

What can be said about the power being dissipated by  and ?

Possible Answers:

will dissipate more power than

Their values will be equal

None of these

 will dissipate more power than

It is impossible to tell

Correct answer:

Their values will be equal

Explanation:

 and are in series with each other, therefore, they will have the same current values. They also have the same resistance values. Thus, they will have the same power dissipated, as .

Example Question #4 : Circuit Power

3 sets of parallel resistors

Calculate the power being dissipated by

Possible Answers:

None of these

Correct answer:

Explanation:

The first step is to find the total resistance of the circuit.

In order to find the total resistance of the circuit, it is required to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with with with .

 

Then, combining  with  and :

Ohms is used law to determine the total current of the circuit

Combing all voltage sources for the total voltage.

 

Plugging in given values,

 

 

We know that the voltage drop across parallel resistors must be the same, so:

Using ohms law:

 

It is also true that:

Using Subsitution:

Solving for :

 Plugging in values:

 

Using the definition of electric power, where is current and is the resistance of the component in question.

 

Example Question #11 : Circuit Power

3 sets of parallel resistors

Calculate the power being dissipated by

Possible Answers:

None of these

Correct answer:

Explanation:

The first step is to find the total resistance of the circuit.

In order to find the total resistance of the circuit, it is required to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with with with .

 

Then, combining  with  and :

Ohms is used law to determine the total current of the circuit

Combing all voltage sources for the total voltage.

 

Plugging in given values,

 

 

It is true that the voltage drop across parallel resistors must be the same, so:

Using ohms law:

 

It is also true that:

Using Subsitution:

Solving for :

Pluggin in values:

 

 Using the definition of electric power, where  is current and is the resistance of the component in question.

Example Question #251 : Electricity And Magnetism

3 sets of parallel resistors

Calculate the power being dissipated by

Possible Answers:

None of these

Correct answer:

Explanation:

The first step is to find the total resistance of the circuit.

In order to find the total resistance of the circuit, it is required to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with with with .

 

Then, combining  with  and :

Ohms is used law to determine the total current of the circuit

Combing all voltage sources for the total voltage.

 

Plugging in given values,

 

 

It is true that the voltage drop across parallel resistors must be the same, so:

Using ohms law

 

It is also true that:

 

 Using Subsitution:

 

 Solving for :

 

 Plugging in values:

 

 Using the definition of electrical power, where is current and is the resistance of the component in question.

 

Example Question #11 : Circuit Power

3 sets of parallel resistors

Calculate the power being dissipated by

Possible Answers:

None of these

Correct answer:

Explanation:

The first step is to find the total resistance of the circuit.

In order to find the total resistance of the circuit, it is required to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with with with .

 

Then, combining  with  and :

Ohms is used law to determine the total current of the circuit

Combing all voltage sources for the total voltage.

 

Plugging in given values,

 

 

It is true that the voltage drop across parallel resistors must be the same, so:

Using ohms law

 

It is also true that:

 

 Using Subsitution:

 Solving for :

 

Pluggin in values:

 

Using the definition of electrical power, where is current and is the resistance of the component in question:

Example Question #14 : Circuit Power

Three parallel resistors

What is the power being dissapaited by ?

Possible Answers:

None of these

Correct answer:

Explanation:

, , and are in parallel, so they are added by using:

Plugging in given values:

, , and  are in series. So they are added conventionally:

Plugging in values:

First, it is necessary to find the total current of the circuit. Using Ohm's law:

 

Solving for :

The total current of the circuit is also the current through

 Using the definition of electric power, where is current and is the resistance of the component in question:

 

Example Question #11 : Circuit Power

Three parallel resistors

What is the power being dissapaited by ?

Possible Answers:

None of these

Correct answer:

Explanation:

, , and are in parallel, so they are added by using:

Plugging in given values:

, , and  are in series. So they are added conventionally:

Plugging in values:

First, it is necessary to find the total current of the circuit. Using Ohm's law:

 

Solving for :

Because and  are in parallel,

Also, the voltage drop must be the same across all three since they are in parallel.

Using Ohm's law again and substituting:

Using algebraic subsitution:

Solving for :

Plugging in values:

 

 Using the definition of electric power, where is current and is reistance.

 

Example Question #92 : Circuit Properties

Three parallel resistors

What is the power being dissapaited by ?

Possible Answers:

None of these

Correct answer:

Explanation:

, , and are in parallel, so they are added by using:

Plugging in given values:

, , and  are in series. So they are added conventionally:

Plugging in values:

First, it is necessary to find the total current of the circuit. Using Ohm's law:

 

Solving for :

Because and  are in parallel,

Also, the voltage drop must be the same across all three since they are in parallel.

Using Ohm's law again and substituting:

Using algebraic subsitution:

Solving for

 

 Plugging in values:

 

 Using the definition of electrical power, where is the current and is the resistance of the component in question:

 

Example Question #91 : Circuit Properties

Three parallel resistors

What is the power being dissapaited by ?

Possible Answers:

None of these

Correct answer:

Explanation:

, , and are in parallel, so they are added by using:

Plugging in given values:

, , and  are in series. So they are added conventionally:

Plugging in values:

First, it is necessary to find the total current of the circuit. Using Ohm's law:

 

Solving for :

Because and  are in parallel,

Also, the voltage drop must be the same across all three since they are in parallel.

Using Ohm's law again and substituting:

Using algebraic subsitution:

Solving for

Plugging in values

Using the definition of electrical power, where is current and is the resistance of the component in question:

 

 Plugging in values

 

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