2016 AP Physics 1 Free Response #4

Allen Tsao The STEM Coach
20 Sept 201806:02
EducationalLearning
32 Likes 10 Comments

TLDRIn this educational video, Alan from Bothwell STEM Coach tackles AP Physics, specifically question four from the 2016 exam. He explains how to rank the potential differences across four identical resistors in a circuit with a battery. Alan uses the analogy of water flow to describe the current splitting in a parallel circuit, leading to different voltage drops across resistors. He clarifies that resistors A and D have the same potential difference, which is greater than that of B and C. He further discusses the effects of removing resistor B on the current through resistor A and C, emphasizing the increase in total resistance and the consequential decrease in current. The video concludes with a brief overview of the scoring guidelines, offering a practical approach to understanding circuit analysis in physics.

Takeaways
  • 🔋 The video discusses an AP Physics question involving a circuit with a battery and four identical resistors.
  • 💡 Alan, the Bothwell stem coach, explains how to rank the voltage drops across resistors from greatest to least.
  • 🌊 The current in the circuit is likened to water flow, which splits between two paths due to the parallel resistors.
  • 🔄 The current splits in half because the two resistances are in parallel, leading to equal likelihood of current taking either path.
  • ⚡ Resistors A and D each have the full current I flowing through them, resulting in a greater voltage drop compared to B and C.
  • 📉 Resistors B and C have half the voltage drop because they only have half the current flowing through them, despite having the same resistance.
  • 🔄 The voltage drop across any resistor is given by the formula \( V = I \times R \).
  • 🔄 Removing resistor B from the circuit increases the total resistance, as the parallel path is no longer present.
  • 📉 The total current decreases when the total resistance increases, as per Ohm's law \( I = V / R \).
  • 🔽 The current through resistor A decreases when B is removed, as the total current is reduced.
  • 🔼 The current through resistor C increases when B is removed, as C now takes all the current that was previously split.
  • 📝 Alan suggests that while the explanation was intuitive, a more analytical approach can be found in the solution guides.
  • 📚 The scoring guidelines confirm that A equals D is greater than B equals C, and the current through A decreases when B is removed.
  • 🎓 Alan offers free homework help on Twitch or Discord for those with questions in math and physics.
Q & A

  • What is the topic of the video?

    -The video discusses a question from the 2016 AP Physics exam, specifically focusing on a circuit with a battery and four identical resistors.

  • What is the main task in the question from the AP Physics exam?

    -The main task is to rank the voltage drops across each resistor from greatest to least, considering the arrangement of the resistors in the circuit.

  • How does the video describe the flow of current in the circuit?

    -The video describes the current flow as splitting between two paths, with the current splitting in half because the two resistances are parallel.

  • Why does the video say that resistors A and D have the same voltage drop as each other?

    -Resistors A and D have the same voltage drop because they each have the full current I flowing through them, as per Ohm's law (V = IR).

  • What is the relationship between the voltage drops across resistors B and C according to the video?

    -The voltage drops across resistors B and C are equal to each other but less than that of A and D, as they each have half the current flowing through them.

  • What happens to the total resistance of the circuit when resistor B is removed?

    -The total resistance of the circuit increases because the parallel path that reduced the resistance is no longer present.

  • How does the removal of resistor B affect the current through resistor A?

    -The current through resistor A remains the same because it is not affected by the removal of resistor B.

  • What is the effect on the current through resistor C when resistor B is removed?

    -The current through resistor C increases because it now takes all the current that was previously split between B and C.

  • What is the video's explanation for the increase in current through C after B is removed?

    -The total current in the circuit decreases, but since C now takes all the current, the increase in current through C compensates for the decrease in total current.

  • What additional resources does the video offer for learning more about physics and math?

    -The video offers free homework help on Twitch or Discord for those who have questions or want to learn more about different parts of math and physics.

  • What is the conclusion of the video regarding the ranking of voltage drops across the resistors?

    -The conclusion is that the voltage drops are ranked as A equals D, which is greater than B equals C.

Outlines
00:00
🔋 Understanding Circuits and Resistors in AP Physics

In this segment, Alan from Bothwell Stem Coach discusses AP Physics, specifically question four from the 2016 exam. The question involves a circuit with a battery and four identical resistors. Alan explains the concept of current flow and resistance in a parallel circuit, illustrating how the current splits between two paths and the resulting voltage drops across the resistors. He clarifies that resistors A and D have the full current flowing through them, resulting in a greater voltage drop compared to resistors B and C, which only have half the current. The explanation is intuitive, focusing on the analogy of current flow similar to water, and the effects of removing a resistor on the total resistance and current in the circuit.

05:05
📉 Impact of Removing a Resistor on Circuit Current

This paragraph delves into the implications of removing resistor B from the circuit. Alan explains that the total resistance increases because the parallel path is reduced, which in turn affects the total current flowing through the circuit. He provides a detailed analysis of how the current through resistor A decreases due to the increase in total resistance, while the current through resistor C increases as it now takes all the current that was previously split between B and C. Alan also touches on the analytical approach to determine the changes in current and resistance, emphasizing the importance of understanding the fundamental principles of circuit behavior.

Mindmap
Keywords
💡AP Physics
AP Physics refers to the Advanced Placement Physics courses and exams offered by the College Board. It is a high school course that prepares students for college-level physics. In the video, the theme revolves around solving a question from the 2016 AP Physics exam, indicating the educational level and subject matter of the content.
💡Circuit
A circuit is a closed loop through which electric current flows. It is a fundamental concept in physics and electrical engineering. The video discusses a specific circuit with a battery and resistors, which is central to understanding the problem-solving process presented in the script.
💡Resistors
Resistors are components in an electrical circuit that oppose the flow of current. They are crucial in controlling the current and voltage in a circuit. The script describes a circuit with four identical resistors, which is key to the problem at hand, as the question involves ranking the potential difference across each resistor.
💡Potential Difference
Potential difference, also known as voltage, is the work needed per unit of charge to move a test charge between two points. It is a driving force in an electrical circuit. The video's main question asks to rank the potential differences across resistors, which is a measure of the voltage drop across each component.
💡Current
Electric current is the flow of electric charge, often symbolized by 'I'. In the context of the video, current is described as splitting between two paths in the circuit, illustrating how it divides and flows through the resistors, affecting the potential difference across them.
💡Parallel Resistance
When resistors are connected in parallel, their combined resistance is less than the resistance of any individual resistor. In the script, it is mentioned that the resistors are arranged in a way that they are parallel to each other, which affects how the current splits and the potential difference across each resistor.
💡Voltage Drop
Voltage drop is the decrease in voltage across a component as current flows through it. The script explains that resistors A and D have a full voltage drop because the full current 'I' flows through them, while B and C have half the voltage drop due to half the current flowing through them.
💡Total Resistance
Total resistance is the equivalent resistance of a circuit that can be calculated by considering the arrangement of resistors. The video discusses how removing a resistor affects the total resistance of the circuit, which in turn affects the total current flowing through it.
💡Ohm's Law
Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them, represented as V = IR. The script uses Ohm's Law to explain the changes in current when the total resistance of the circuit changes.
💡Scoring Guidelines
Scoring guidelines are used to evaluate the correctness of answers in exams like AP Physics. The script refers to these guidelines to validate the solution to the problem, ensuring that the reasoning provided aligns with the expected understanding of the concept.
💡Homework Help
Homework Help is a service offered by the video creator to assist with homework questions, particularly in math and physics. It is mentioned at the end of the script as an additional resource for viewers, showing the creator's commitment to supporting learning beyond the video content.
Highlights

Continuing AP Physics lesson, focusing on question 4 from the 2016 exam.

Circuit contains a battery and four identical resistors arranged in a specific way.

Task is to rank the voltage drops across each resistor from greatest to least.

If resistors have the same voltage drop, state it explicitly with reasoning.

Current flows and splits between two paths due to parallel resistances.

A and D have full current I flowing through them, so higher voltage drop.

B and C have half the current (1/2 I) flowing, resulting in lower voltage drop.

Voltage drop across a resistor is given by V = I * R.

A and D are equal in voltage drop, greater than B and C which are also equal.

Removing resistor B increases total resistance and decreases total current.

Current through A decreases when B is removed due to increased resistance.

Current through C increases when B is removed, as it takes all the current.

Total resistance with B removed is 3R, higher than original 5R/2.

Current through C increases from V/5R to V/3R when B is removed.

Scoring guidelines confirm A=D > B=C, and current through A decreases, C increases.

Free homework help offered on Twitch or Discord for math and physics questions.

Transcripts

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AP PhysicsCircuit AnalysisResistorsCurrent FlowVoltage DropParallel ResistanceElectrical CurrentPhysics TutorialEducational VideoSTEM CoachHomework Help