Correct energy transformation about circuit with EMF, a resistor and a motor

• songoku
songoku
Homework Statement
Relevant Equations
Energy transformation

My answer is C (although I am not sure if the correct one is C or D). I suppose since the 1-V battery is being charged by the 9-V battery, the electrical energy should be on the RHS of the energy transformation. Am I correct?

Thanks

Given that you think that the correct answer is C, why did you exclude answer A? What's the difference between A and C?

songoku
kuruman said:
Given that you think that the correct answer is C, why did you exclude answer A? What's the difference between A and C?
Because the pulley lifts a load so I think there would be energy converted to GPE, which is not covered by option A

Thanks

What do you understand mechanical energy to be?

Hint: Read the first sentence here.

songoku
kuruman said:
What do you understand mechanical energy to be?

Hint: Read the first sentence here.
I thought the mechanical energy in this case maybe refer to something in the motor or pulley (like rotation). Is it not? So the correct answer should be A?

Thanks

songoku said:
So the correct answer should be A?
Are you asking me or are you telling me? As you know, according to our rules we cannot give answers away.

songoku
kuruman said:
Are you asking me or are you telling me? As you know, according to our rules we cannot give answers away.
I am asking, sorry.

My answer is still the same, it is C and the reasoning is this
songoku said:
I thought the mechanical energy in this case maybe refer to something in the motor or pulley (like rotation)
Is my reasoning not correct?

Thanks

songoku said:
I am asking, sorry.

My answer is still the same, it is C and the reasoning is this

Is my reasoning not correct?

Thanks
I believe if you are adhering to the definition, then gravitational potential is a part of mechanical energy. Do you have definitions given to you of mechanical energy that say otherwise?

songoku
erobz said:
I believe if you are adhering to the definition, then gravitational potential is a part of mechanical energy. Do you have definitions given to you of mechanical energy that say otherwise?
No, I don't. What I learned about mechanical energy is that it is the sum of potential and kinetic energy. I am only using my own interpretation that maybe this is some trick question so I tried to include whatever rotation in motor and pulley to be referred as mechanical energy and gravitational energy is treated separately

Thanks

`IMO none of the given answers are correct and the appropriate answer should be:
chemical → electrical → thermal + mechanical

songoku and nasu
Thank you very much for the help and explanation kuruman, erobz, Steve4Physics

songoku said:
Thank you very much for the help and explanation kuruman, erobz, Steve4Physics
If you remember, let us know what the supposed correct answer was when you find out.

songoku

What is the role of EMF in an electric circuit with a resistor and a motor?

The Electromotive Force (EMF) serves as the energy source in the circuit. It provides the necessary voltage to drive the current through the circuit, powering both the resistor and the motor. Essentially, EMF is responsible for converting chemical or mechanical energy into electrical energy.

How is energy transformed in a circuit with a resistor and a motor?

In such a circuit, the EMF supplies electrical energy. This electrical energy is then partially converted into thermal energy by the resistor due to its resistance, and the remaining energy is converted into mechanical energy by the motor. The motor uses this energy to perform work, such as turning a shaft.

Why does the resistor in the circuit cause energy loss?

The resistor causes energy loss due to the Joule heating effect, where electrical energy is converted into heat. This is an inherent property of resistors, as they impede the flow of current, causing some of the electrical energy to dissipate as thermal energy. This energy loss is often considered undesirable in circuits where efficiency is crucial.

How can we calculate the energy consumed by the motor in the circuit?

The energy consumed by the motor can be calculated using the formula $$P = VI$$, where $$P$$ is the power, $$V$$ is the voltage across the motor, and $$I$$ is the current flowing through the circuit. To find the energy consumed over a period of time, you can use $$E = Pt$$, where $$E$$ is the energy and $$t$$ is the time the motor is running.

What factors affect the efficiency of energy transformation in this circuit?

The efficiency of energy transformation in the circuit is affected by several factors including the resistance of the resistor, the internal resistance of the EMF source, and the efficiency of the motor itself. Higher resistance leads to greater energy loss as heat, and a less efficient motor converts less electrical energy into mechanical energy. Minimizing these losses is key to improving overall efficiency.

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