Discover Energy Changes in a Model Train's Electric Motor and Controller

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Discussion Overview

The discussion revolves around understanding energy changes in a model train's electric motor and controller, focusing on the implications of power distribution and energy transformation within the system. The context includes aspects of homework-related inquiry and technical reasoning regarding electrical energy conversion.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes the current through the motor is 0.5A and the voltage is 5V, leading to a total power of 6W, with specific power values for the motor and controller.
  • Another participant points out the need for a specified time period to calculate energy changes, referencing the formula E = P * t.
  • Some participants express confusion regarding the question's clarity, particularly the lack of a time frame for energy calculations.
  • One participant suggests that the question may be asking about the transformation of electrical energy by the motor or the controller.
  • There is a repeated emphasis on the need for clarification from the professor or TA regarding the question's intent.

Areas of Agreement / Disagreement

Participants generally agree on the confusion surrounding the question's requirements, particularly regarding the time aspect needed for energy calculations. However, there is no consensus on the interpretation of what the energy changes refer to, leading to multiple competing views.

Contextual Notes

The discussion highlights limitations in the provided question, particularly the absence of a time variable necessary for energy calculations and the ambiguity in what specific energy changes are being asked about.

Who May Find This Useful

This discussion may be useful for students working on similar homework problems related to electrical energy transformations in circuits, particularly in understanding the role of time in energy calculations.

Rapidfire
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A model train has an electric motor to drive it. The current though the motor is controlled by a rheostat and when it is moving slowly the current is 0.5A and the voltage is 5V.

Data
Total Power = 6W
Power Developed By Motor = 2.5W
Power Absorbed By Controller = 3.5W

Total Voltage = 12V
Voltage Across Motor = 5V
Voltage Across Controller = 7V

Current = 0.5A

Question
Find the energy changes in:
1. The controller
2. The motor

Circuit Diagram
Below is my diagram sketch of the circuit. Just click the link to look at it. It is a little rough but it should help you to understand my circuit.
 

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Moved to homework forum. Please be sure to post all homework questions in the homework forums, and show some of your work so that we can help you.

"Find the energy changes in the motor and controller" when what happens? When the rheostat is changed to some other setting? And to calculate energy, you need some time period specified, since E = P * t.

Can you please post the full Question, word-for-word?
 
The question just says what is the energy change. The reason I am stuck is because it doesn't give me a time to work out energy. I know the formula EPT.
 
Rapidfire said:
The question just says what is the energy change. The reason I am stuck is because it doesn't give me a time to work out energy. I know the formula EPT.

Sorry, that makes no sense to me. Any chance you can ask the prof or TA for clarification?
 
Well I just worked out it means what the electrical energy changes to.
 
Rapidfire said:
Well I just worked out it means what the electrical energy changes to.
Are you asking what a resistor turns electrical energy into?
Or what a motor does with electrical energy?
 

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