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

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A model train's electric motor operates with a current of 0.5A and a voltage of 5V, resulting in total power consumption of 6W, with the motor developing 2.5W and the controller absorbing 3.5W. The voltage across the motor is 5V, while the controller experiences 7V. The discussion revolves around calculating energy changes in both the motor and controller, highlighting the need for a specified time period to apply the energy formula E = P * t. Participants express confusion over the question's lack of clarity regarding the time factor and the nature of energy transformations. Clarification from a professor or TA is suggested to better understand the energy changes involved.
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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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