2023 AP Physics 2 Free Response #2

Allen Tsao The STEM Coach

14 May 202312:08

EducationalLearning

32 Likes 10 Comments

TLDRThe video script from a 2023 AP Physics 2 exam walkthrough explores an experiment to identify whether a component is a resistor or an uncharged capacitor. It suggests using a battery source and a voltmeter to measure voltage across the component over time. If the component is a capacitor, the voltage should increase to the battery's voltage as it charges. The script also covers calculating the EMF of a non-ideal battery with internal resistance using Ohm's law and plotting data to find the slope and y-intercept, ultimately determining the EMF.

Takeaways

🔬 The video discusses the second free response question from the 2023 AP Physics 2 exam, focusing on experimental procedures to identify components like resistors and uncharged capacitors.
🔋 The method involves using standard circuit equipment to measure voltage and current to determine the nature of the component.
🔌 To identify an uncharged capacitor, one should observe the voltage leveling off or the current dropping to zero, indicating the component's behavior under charge and discharge.
🔄 The procedure includes connecting a voltage source and a voltmeter in parallel to measure the potential difference across the component.
⏱ The experiment involves recording the voltage across the circuit component over time and repeating the process multiple times to observe consistent behavior.
🌐 The script mentions grounding or shorting the circuit component to discharge it, simulating the behavior of an uncharged capacitor.
📊 Data collection involves measuring the current through the circuit for different values of a variable resistor, which helps in understanding the battery's EMF and internal resistance.
⚡ The loop equation derived in the script relates the voltage source to the voltage drops across the internal resistance and the variable resistor, using Ohm's law.
📈 To find the EMF of the battery, the script suggests plotting 1/I (reciprocal of current) against the variable resistor (Rver) to yield a straight line, from which the slope and y-intercept can be used to calculate EMF.
📚 The script provides an example of how to manipulate algebraic expressions to find a suitable format for plotting data that allows for the calculation of the battery's EMF.
📉 The video concludes with the calculation of the EMF using the slope of the plotted line, demonstrating the application of the derived equation in practical data analysis.

Q & A

What is the main task students are asked to perform in the script?
-The main task is to experimentally determine whether a component is a resistor or an uncharged capacitor using standard circuit equipment.
How can one initially distinguish between a resistor and an uncharged capacitor in a circuit?
-By observing the voltage and current levels; an uncharged capacitor should show a leveling off of the voltage or a decrease in current to zero over time.
What is the first step in the experimental procedure described in the script?
-The first step is to hook up a battery source and measure the voltage across the unknown component.
Why is it important to use a voltmeter in parallel when measuring the potential difference across a component?
-A voltmeter must be connected in parallel to measure the potential difference accurately because it needs to be across the component without altering the circuit's current flow.
What should be expected if the component under test is an uncharged capacitor?
-If the component is an uncharged capacitor, the voltage observed should start at zero and increase to the battery's voltage as the capacitor charges.
What is the significance of discharging the circuit component by grounding?
-Discharging by grounding ensures that the component is back to its initial state (uncharged) before repeating the experiment, providing consistent results.
In the script, what is the purpose of plotting 1/I against Rver?
-Plotting 1/I against Rver helps to determine the EMF of the battery and its internal resistance by creating a straight line where the slope and y-intercept can be used for calculations.
What is the equation derived from the loop equation that relates E, I, R, and Rver?
-The derived equation is E = I(R + Rver), which can be rearranged to find the relationship between the variables for plotting purposes.
How can one find the EMF of the battery using the graph?
-By calculating the slope of the line on the graph, where 1/Epsilon equals the slope, and then taking the reciprocal to find the EMF value.
What is the approximate EMF value of the battery calculated from the graph in the script?
-The approximate EMF value of the battery is 20 volts, as determined by the slope of the graph.

Outlines

00:00

🔬 Experimental Determination of Circuit Components

This paragraph discusses an experiment from the 2023 AP Physics 2 exam to identify whether a component is a resistor or an uncharged capacitor. The procedure involves connecting a battery source and a voltmeter in parallel to measure the voltage across the component. The expected behavior of an uncharged capacitor is that the voltage should start at zero and increase to the battery's voltage as it charges. The paragraph also mentions an experiment to determine the EMF of a non-ideal battery with internal resistance, where students collect data on current through the circuit for different values of a variable resistor.

05:00

📈 Data Analysis and Graph Plotting for EMF Calculation

The second paragraph focuses on analyzing data collected from an experiment involving a non-ideal battery and a variable resistor. The goal is to derive an equation that describes the relationship between the current (I), the internal resistance (r), and an external variable resistor (R_ver). The paragraph outlines the process of plotting 1/I against R_ver to find a straight line, from which the slope and y-intercept can be used to calculate the EMF of the battery. The speaker provides a step-by-step guide on how to transform the equation, plot the data, and calculate the slope and y-intercept to find the EMF.

10:03

📊 Graph Interpretation and EMF Determination

In the final paragraph, the speaker attempts to draw a line on a graph to determine the EMF of the battery by interpreting the plotted data. The process involves selecting points from the graph, calculating the slope, and using this to find the EMF value. The speaker acknowledges the difficulty of the task due to the limitations of the graphing tool used. After adjusting the line and selecting points, the slope is calculated, and the EMF is determined to be approximately 20 volts.

Mindmap

Keywords

💡AP Physics 2 exam

The AP Physics 2 exam is a standardized test offered by the College Board for high school students to demonstrate their understanding of advanced physics concepts. In the video, the script discusses the second free response question from the 2023 exam, indicating its relevance to the educational context and the focus on problem-solving in physics.

💡Experimental procedure

An experimental procedure refers to a step-by-step method used to conduct a scientific experiment. In the script, the speaker outlines a procedure to determine whether a component is a resistor or an uncharged capacitor, emphasizing the importance of systematic investigation in understanding physical phenomena.

💡Resistor

A resistor is a passive component in an electrical circuit that opposes the flow of current. The video script describes an experiment to identify a resistor by measuring voltage and current, highlighting the role of resistors in controlling electrical current.

💡Uncharged capacitor

An uncharged capacitor is a component that has no stored electrical charge. The script explains that if the component is an uncharged capacitor, the voltage should level off as it charges, illustrating the concept of capacitance and its behavior in a circuit.

💡Circuit equipment

Circuit equipment refers to the tools and components used to build and analyze electrical circuits. The video mentions using standard circuit equipment to determine the nature of a component, such as a battery source and voltmeter, which are essential for conducting the described experiments.

💡Voltage

Voltage, also known as electric potential difference, is the force that pushes electric charge through a conductor. The script discusses measuring voltage across a component to identify its type, showing voltage as a key parameter in electrical experiments.

💡Current

Electric current is the flow of electric charge in a circuit. The video script mentions measuring the current to determine if a component is a resistor or an uncharged capacitor, indicating the role of current in circuit analysis.

💡EMF (Electromotive Force)

Electromotive Force (EMF) is the energy provided by a power source to drive an electric current through a circuit. The script involves an experiment to determine the EMF of a battery, which is crucial for understanding the power source's characteristics and its role in the circuit.

💡Internal resistance

Internal resistance is the resistance within a power source that opposes the flow of current. The video script describes a battery with internal resistance, which is an important factor in analyzing the performance of the battery and the circuit.

💡Variable resistor

A variable resistor, also known as a potentiometer, is a component that allows for the adjustment of resistance in a circuit. The script discusses using a variable resistor to collect data on current for different resistance values, demonstrating the use of variable resistors in experimental setups.

💡Data collection

Data collection is the process of gathering information and measurements for analysis. In the script, the speaker describes collecting data on current for various resistance values, which is a fundamental step in conducting experiments and drawing conclusions.

💡Graph

A graph is a visual representation of data, often used to identify patterns or relationships. The video script involves plotting data to yield a straight line, which can be used to calculate the numerical value of EMF, illustrating the importance of graphical analysis in interpreting experimental results.

Highlights

Students are asked to experimentally determine whether a component is a resistor or an uncharged capacitor using standard circuit equipment.

To identify an uncharged capacitor, measure the voltage across it and observe if it levels off, or measure the current which should level off to zero.

Connect a voltage source and voltmeter in parallel to measure the potential difference across the circuit component.

Record the voltage across the circuit component over time and repeat the process multiple times to observe changes.

Discharge the circuit component by grounding it to reset for repeated measurements.

If the component is an uncharged capacitor, expect the voltage to start at zero and increase to the battery voltage as it charges.

Connect a battery with internal resistance to a variable resistor and measure the current for different resistor values.

Write an equation describing the relationship between voltage, current, internal resistance, and variable resistor.

The loop equation states that the voltage source equals the sum of voltage drops across the internal and variable resistors.

To find the EMF of the battery, rearrange the equation to isolate the current and express it in terms of the slope and y-intercept.

Plot 1/I vs. Rver on a graph to yield a straight line, where the slope and y-intercept can be used to calculate the EMF.

The reciprocal of the current (1/I) should be plotted on the y-axis and the variable resistor value (Rver) on the x-axis.

Compute the values of 1/I for the collected data to create the y-axis values for the graph.

Estimate the EMF by determining the slope of the best-fit line on the 1/I vs. Rver graph.

The slope of the line is inversely proportional to the EMF, so calculate the EMF by taking the reciprocal of the slope.

Use two points on the graph to calculate the slope and determine the EMF value.

The estimated EMF of the battery is approximately 20 volts based on the graph and slope calculation.

Transcripts

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