AP Physics 2 : Current and Voltage

Study concepts, example questions & explanations for AP Physics 2

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Example Questions

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Example Question #1 : Current And Voltage

A  battery produces a  current in a piece of wire. What is the resistance of the wire?

Possible Answers:

There's not enough information to determine the resistance of the wire

Correct answer:

Explanation:

The relevant equation for this problem is Ohm's law.

We're given the voltage and the current, so we need to rearrange to get the resistance.

Example Question #2 : Current And Voltage

Consider a circuit connected to a  battery that has a resistance of . How many moles of charge pass through this circuit within a 30s period?

Possible Answers:

Correct answer:

Explanation:

To begin with, we'll need to calculate the current that is flowing through this circuit. We can do this by using Ohm's law.

Now that we have an expression that gives us the current, which is in units of charge per second, we'll need to calculate the moles of charge per second.

This expression directly above gives the total amount of charge that passes within a given time frame. But to find the moles of charge, we'll need to use Faraday's constant.

Example Question #3 : Current And Voltage

3 sets of parallel resistors

 

Determine the current through .

Possible Answers:

Correct answer:

Explanation:

First, we need to find the total resistance of the circuit. In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: 

 

Then, we will need to use Ohms law to determine the total current of the circuit

Combine all of our voltage sources: 

Plug in our values:

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

Use Ohm's law:

We also know that:

Substitute:

Solve for :

Example Question #4 : Current And Voltage

3 sets of parallel resistors

 

Determine the current through .

Possible Answers:

Correct answer:

Explanation:

First, we need to find the total resistance of the circuit. In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: 

Then, we will need to use Ohm's law to determine the total current of the circuit: 

Combine all of our voltage sources: 

Plug in our values:

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

Use Ohm's law:

We also know that:

Substitute: 

Solving for :

We plug in our values:

Example Question #5 : Current And Voltage

3 sets of parallel resistors

 

Determine the current through .

Possible Answers:

Correct answer:

Explanation:

First, we need to find the total resistance of the circuit. In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: 

Then, we will need to use Ohms law to determine the total current of the circuit.

 

Combine all of our voltage sources: 

Plug in our values:

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

Use Ohm's law:

We also know that:

Substitute: 

Solve for :

Plug in our values:

Example Question #6 : Current And Voltage

3 sets of parallel resistors

 

Determine the current through .

Possible Answers:

Correct answer:

Explanation:

First, we need to find the total resistance of the circuit. In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: 

Then, we will need to use Ohm's law to determine the total current of the circuit.

Combine all of our voltage sources:

Plugin our values:

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

Use Ohm's law:

We also know that:

Substitute: 

Solving for :

Plug in our values:

Example Question #7 : Current And Voltage

3 sets of parallel resistors

 

Determine the current through .

Possible Answers:

Correct answer:

Explanation:

First, we need to find the total resistance of the circuit. In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: 

Then, we will need to use Ohm's law to determine the total current of the circuit.

 

Combine all of our voltage sources: 

Plug in our values:

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

Use Ohm's law:

We also know that:

 

Substitute: 

Solve for :

Plug in our values:

Example Question #8 : Current And Voltage

3 sets of parallel resistors

 

Determine the current through .

Possible Answers:

Correct answer:

Explanation:

First, we need to find the total resistance of the circuit. In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: 

Then, we will need to use Ohm's law to determine the total current of the circuit.

Combine all of our voltage sources:

Plug in our values:

 

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

 

Use Ohm's law:

We also know that: 

Substitute: 

Solve for :

Plug in our values:

.

Example Question #9 : Current And Voltage

3 sets of parallel resistors

 

Determine the voltage drop across .

Possible Answers:

Correct answer:

Explanation:

First, we need to find the total resistance of the circuit. In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: 

Then, we will need to use Ohm's law to determine the total current of the circuit

Combine all of our voltage sources:

Plug in our values:

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

Use Ohm's law:

We also know that:

Substitute:

Solve for :

We plug in our values.

Use Ohm's law:

Example Question #34 : Circuit Properties

3 sets of parallel resistors

 

Determine the voltage drop across .

Possible Answers:

Correct answer:

Explanation:

First, we need to find the total resistance of the circuit. In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: 

Then, we will need to use Ohm's law to determine the total current of the circuit. 

Combine all of our voltage sources: 

Plug in our values:

 

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

Using Ohm's law:

We also know that:

Substitute:

Solving for :

Plug in our values:

Use Ohm's law:

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