# Stuck With Energy Changes!

Info
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.

#### Attachments

• 6.6 KB Views: 130
Last edited:

Related Engineering and Comp Sci Homework Help News on Phys.org
berkeman
Mentor
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.

berkeman
Mentor
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.

NoTime