AP Physics 1 : Current and Voltage

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #201 : Electricity And Waves

Give the SI units for voltage. 

Possible Answers:

Correct answer:

Explanation:

We have to know what SI units are for this problem. SI units are units that cannot be broken down into smaller component parts. Voltage  is defined as: 

, where  is joules and  is Coulombs. Coulombs are already in SI units. However, joules is composed of other terms. 

Therefore, voltage can be written as

Example Question #132 : Electricity

 of charge pass through a television during a  movie.  How much is being used by the television?

Possible Answers:

Correct answer:

Explanation:

Current and charge are related by the equation  where  is the current in Amperes (),  is the charge in Coulombs (), and  is the time in seconds ().

Time must first be converted to seconds.

Solving for current,

Example Question #133 : Electricity

Who long (in hours) does it take a computer to use  of charge ?

Possible Answers:

Correct answer:

Explanation:

Current and charge are related by the equation  where  is the current in Amperes (),  is the charge in Coulombs (), and  is the time in seconds ().

For this problem

Example Question #134 : Electricity

What quantity of charge passes through a clock in  if its current is ?

Possible Answers:

Correct answer:

Explanation:

Current and charge are related by the equation  where  is the current in Amperes (),  is the charge in Coulombs (), and  is the time in seconds ().

Time must first be converted to seconds.

Solving for charge,

.

Example Question #1361 : Ap Physics 1

A circuit with one battery and one resistor with resistance  has current  flowing through it. It is modified to add two more identical resistors in series of the first resistor and 1 more resistor in parallel to the other three with resistance . Determine the current flowing through the original resistor. 

Possible Answers:

Correct answer:

Explanation:

To find our answer, we have to know how each of the new additions changes the circuit. The addition of the two resistors in series do not affect the current because current is equivalent for resistors in series. However, since there is a resistor in parallel with equivalent resistance to the sum of the 3 resistors in series, current will split evenly amongst the two pathways, thus leading to a current of  flowing through the original resistor. 

Example Question #135 : Electricity

Consider a circuit composed of a  battery and three resistors in series. The three resistors are . Calculate the voltage drop  across .

Possible Answers:

Correct answer:

Explanation:

In order to find the voltage drop  across , we will use Ohm's law: 

.

However, we first need to solve for the current  in the circuit. This will be calculated by applying Ohm's law to the entire circuit, using the total resistance  for resistors in series. 

Finally, we use this calculated current to find the voltage drop across .

Example Question #202 : Electricity And Waves

Determine the voltage drop across a resistor of  experiencing a  current flowing through it, if it is connected to a battery of ?

Possible Answers:

Correct answer:

Explanation:

In circuits with resistors, the only thing necessary to determine voltage drop across a resistor is the current through it and the resistance, as given by Ohm's law. 

Example Question #211 : Electricity And Waves

You have the following circuit. The values for the components are:

Circuit

What is the current passing though R3?

Possible Answers:

Correct answer:

Explanation:

The first step is to find the equivalent resistance of the entire circuit. Note that R2 and R3 are in parallel, and they are in series with R1. Therefore, in order to find the equivalent resistance:

Then, in order to find the total current, use Ohm's Law:

That means that  will pass through R1, and will split when it reaches the junction between R2 and R3 based on the ratio of the two resistance:

 of current passes through the resistor R3.

Example Question #212 : Electricity And Waves

Which of the following wires with a current running through them would have the least resistance?

Possible Answers:

They would all have equal resistance

Wire B:  and 

Wire C:  and 

Wire D:  and 

Wire A:  and 

Correct answer:

Wire B:  and 

Explanation:

The correct answer is Wire B with  and  of current.

The formula for voltage, current and resistance is as follows:

Thus, the wire with the lowest ratio of voltage to current will have the least resistance.

Example Question #11 : Current And Voltage

Series curcuit

What is the current in the given circuit if  and ?

Possible Answers:

Correct answer:

Explanation:

To find the current we must first find the equivalent resistance. For resistors in series, the equivalent resistance is 

For this problem

Now we use Ohm's law, , to find the current, 

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