Energies - chemical and electrical (easy question)

[Melawrghk]

I have to graph changes in energies. And I have a question - so I have a battery that supplies power to a motor and some sensors. I have to assume it starts with 36000J of energy (chemical energy, right?). Then, pretend a motor uses 22J and shuts off. Now I would have 35978J of chemical left. But what about electrical? Is it the same as chemical in this case? Or is it equivalent to just the value of chemical used? So 22J...

Also, I know the motor is 5% efficient. So if I know how much work it did on a certain item, would I have to multiply it by 20 to get the change in chemical energy?

Thanks bunches :)

 

[CEL]

I have to graph changes in energies. And I have a question - so I have a battery that supplies power to a motor and some sensors. I have to assume it starts with 36000J of energy (chemical energy, right?). Then, pretend a motor uses 22J and shuts off. Now I would have 35978J of chemical left. But what about electrical? Is it the same as chemical in this case? Or is it equivalent to just the value of chemical used? So 22J...

Supposing 100% efficiency, 22J of chemical energy are turned into 22J of electrical energy by the battery, then into 22J of mechanical energy by the motor.

Also, I know the motor is 5% efficient. So if I know how much work it did on a certain item, would I have to multiply it by 20 to get the change in chemical energy?

Thanks bunches :)

Yes, and 19 x 22J of chemical energy are turned into the same amount of thermal energy.

 

[Mene]

Hello,

Thank you for your question. First of all, you are correct that the initial energy supplied by the battery is chemical energy, which is stored in the battery's chemical bonds. As the battery supplies power to the motor and sensors, this chemical energy is converted into electrical energy, which is then used to power the motor and sensors.

In terms of graphing changes in energies, you would need to plot both the chemical and electrical energies over time. Since the battery is supplying a constant amount of energy (36000J), the chemical energy line on the graph would remain constant until the motor shuts off and the chemical energy decreases by 22J. At the same time, the electrical energy line would increase as the battery's chemical energy is converted into electrical energy to power the motor.

To answer your second question, the electrical energy is not equivalent to the chemical energy used in this case. The electrical energy is the energy that is being transferred from the battery to the motor and sensors, while the chemical energy is the initial energy stored in the battery. So in your example, the electrical energy would be 22J, while the chemical energy would decrease by 22J to 35978J.

Regarding the motor's efficiency, if you know the amount of work it did on a certain item, you would need to multiply it by 20 to get the change in chemical energy. This is because the motor's efficiency of 5% means that only 5% of the electrical energy is actually converted into mechanical work, while the remaining 95% is lost as heat. Therefore, to calculate the change in chemical energy, you would need to account for this efficiency by multiplying the work done by 20.

I hope this helps clarify your questions. Let me know if you have any further questions. Good luck with your graphing!