AP Physics 1 : Electricity

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #2 : Understanding Circuit Diagrams

Circuit diagram

 

In the circuit above, what is the total voltage?

Possible Answers:

Correct answer:

Explanation:

To find the voltage, first find the combined resistances of the resistors in parallel:

Use Ohm's law to find the voltage.

Example Question #3 : Understanding Circuit Diagrams

Circuit diagram

In the circuit above, what is the resistance of ?

Possible Answers:

Correct answer:

Explanation:

Find the total resistance of the circuit, which can be determined using Ohm's law.

Now, the resistance of the second resistor can be found. Since the two resistors are in parallel, they're related to the total resistance as follows:

Rearrange and solve for 

Example Question #5 : Understanding Circuit Diagrams

Circuit diagram2

In the circuit above, what is the total resistance?

Possible Answers:

Correct answer:

Explanation:

Find the combined resistances for the resistors in parallel:

Combine these two combined series resistors to find the total resistance:

 

Example Question #4 : Understanding Circuit Diagrams

Circuit diagram2

In the circuit above, what is the voltage drop across ?

Possible Answers:

Correct answer:

Explanation:

Find the total resistance of the circuit. First, calculate the values of the combined resistances of the resistors in parallel:

Therefore, the total resistance is:

Now, note that since  and  are in parallel, the voltage drop across them is the same. Use Ohm's law to relate current in terms of voltage and resistance.

Substitute into Ohm's law for the resistance across :

Example Question #1311 : Ap Physics 1

Circuit diagram2

In the circuit above, what is the current passing through ?

Possible Answers:

Correct answer:

Explanation:

Find the total resistance of the circuit. First, calculate the values of the combined resistances of the resistors in parallel:

Therefore, the total resistance is:

From Ohm's law, we know that  is the current traveling through the circuit.

This current will be divided between  and , with more current taking the path of lower resistance. 

Total voltage drop across :

The current through  is given by:

Example Question #11 : Understanding Circuit Diagrams

Circuitdiagram3

In the circuit above, what is the total resistance?

Possible Answers:

Correct answer:

Explanation:

Begin by combining the resistors that are immediately in series:

Circuit diagramab

Now to find the total resistance, combine these two new resistance values, which are in parallel:

Example Question #11 : Understanding Circuit Diagrams

Circuitdiagram3

In the circuit above, what is the voltage drop across ?

Possible Answers:

Correct answer:

Explanation:

To approach this problem, note that there are no other resistors (or combinations or resistors) beyond the parallel arrangement shown, so the voltage drop across the top  and the bottom  is the same and equal to the voltage across the circuit, .

The voltage drop across  can be found as:

Example Question #12 : Understanding Circuit Diagrams

Circuitdiagram3

In the circuit above, what is the current passing through ?

Possible Answers:

Correct answer:

Explanation:

To approach this problem, note that there are no other resistors (or combinations or resistors) beyond the parallel arrangement shown, so the voltage drop across the top  and the bottom  is the same and equal to the voltage across the circuit, .

Furthermore, the current that passes through  must be the same as the current that passes through .

Therefore, the current that passes through them can be found by rearranging Ohm's law, solving for current.

Example Question #13 : Understanding Circuit Diagrams

Basic circuit2

In the circuit above:

What is the current across ?

Possible Answers:

Correct answer:

Explanation:

The quickest way to approach this problem is to realize that the voltage drop across  is the same as the voltage drop across the combined resistances of  and . Since this parallel combination is the only presence of resistance in the circuit, this voltage drop must be the total voltage of the circuit, .

Therefore, the current across  is:

Example Question #14 : Understanding Circuit Diagrams

Basic circuit2

In the circuit above:

What is the current across ?

Possible Answers:

Correct answer:

Explanation:

Realize that the voltage drop across the combined resistances of  and  must be equal to the voltage of the circuit, since the parallel combination is the only presence of resistance in the circuit. This voltage drop must be the total voltage of the circuit, .

The current across  and  is the same, and is given as:

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