Energy Transfers

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Energy Transfers

Postby sperlman » November 6th, 2014, 4:40 am

Is using a battery to power a circuit a legal Chemical to Electrical transfer? If not, what are some suggestions of things that are?

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Re: Energy Transfers

Postby bernard » November 6th, 2014, 8:58 am

Is using a battery to power a circuit a legal Chemical to Electrical transfer? If not, what are some suggestions of things that are?
For the battery to count as chemical energy, you would have to make it yourself. However, all batteries must be factory sealed, which disallows you from making your own.

Dissociated ionic compounds, such as table salt, in water are electrolytes and conduct electricity.
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Re: Energy Transfers

Postby goodcheer » December 20th, 2014, 11:45 am

In another thread, it has been mentioned that a relay switch has a self-contained sequence of energy transfers: that is, it starts with electrical energy, goes to mechanical by means of an electromagnetic switch, and then goes back to electrical. Thus the ETS would be E-M-E. Another device which has a self-contained ETS is a thermocouple. It starts with thermal energy, goes to electrical, then to mechanical; thus T-E-M. It would be doubtful that you could use these devices for a complete ETS (unless you made your own), but it seems you could certainly use them as part of an ETS.

Also in another thread, photoresistors were mentioned. This is another good example of something that could be used in an ETS. For example, a mechanical switch could turn on a light which would shine on a photoresistor which would turn another circuit on; thus, M-E-VL-E.

What I wonder about is how does a photoresistor work? I have read light gives bound electrons enough energy to jump into the conduction band resulting in an electrical current. I also read something about dissimilar materials being used: would this involve a chemical transfer within the photoresistor or is it considered physical? Also within some applications like a street light, I read heating and cooling causes the switch to work. Would that be a thermal transfer within the photoresistor itself or somewhere else within the light switch?

In a word, this is all amazing! Well, another word: wonderful, what scientific minds can do!

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Re: Energy Transfers

Postby wlmeng11 » December 20th, 2014, 9:29 pm

In another thread, it has been mentioned that a relay switch has a self-contained sequence of energy transfers: that is, it starts with electrical energy, goes to mechanical by means of an electromagnetic switch, and then goes back to electrical. Thus the ETS would be E-M-E. Another device which has a self-contained ETS is a thermocouple. It starts with thermal energy, goes to electrical, then to mechanical; thus T-E-M. It would be doubtful that you could use these devices for a complete ETS (unless you made your own), but it seems you could certainly use them as part of an ETS.

Also in another thread, photoresistors were mentioned. This is another good example of something that could be used in an ETS. For example, a mechanical switch could turn on a light which would shine on a photoresistor which would turn another circuit on; thus, M-E-VL-E.

What I wonder about is how does a photoresistor work? I have read light gives bound electrons enough energy to jump into the conduction band resulting in an electrical current. I also read something about dissimilar materials being used: would this involve a chemical transfer within the photoresistor or is it considered physical? Also within some applications like a street light, I read heating and cooling causes the switch to work. Would that be a thermal transfer within the photoresistor itself or somewhere else within the light switch?

In a word, this is all amazing! Well, another word: wonderful, what scientific minds can do!
Strictly speaking, a thermocouple itself would only be T-E; you may be thinking of some application with a thermocouple and an additional electromechanical device.

A photoresistor is a semiconductor device that makes use of the photoelectric effect, so there wouldn't be any chemical changes involved. "Dissimilar materials" probably refers to the addition of dopants (impurities) to improve the characteristics of a semiconductor (eg. adding phosphorus to make n-type silicon).

w.r.t. the street light, photoresistors aren't designed to operate based on temperature changes, although the resistance typically does vary with temperature. However, it would be quite strange to use a photoresistor to detect temperature changes as something like a thermistor or thermocouple would be more suitable for the task.
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Re: Energy Transfers

Postby goodcheer » December 22nd, 2014, 3:14 pm


Strictly speaking, a thermocouple itself would only be T-E; you may be thinking of some application with a thermocouple and an additional electromechanical device.

A photoresistor is a semiconductor device that makes use of the photoelectric effect, so there wouldn't be any chemical changes involved. "Dissimilar materials" probably refers to the addition of dopants (impurities) to improve the characteristics of a semiconductor (eg. adding phosphorus to make n-type silicon).

w.r.t. the street light, photoresistors aren't designed to operate based on temperature changes, although the resistance typically does vary with temperature. However, it would be quite strange to use a photoresistor to detect temperature changes as something like a thermistor or thermocouple would be more suitable for the task.

Thanks. A Wikipedia article says concerning a street light, "The photoresistor....controls whether current flows through the heater which opens the main power contacts. At night, the heater cools, closing the power contacts, energizing the street light." I am guessing this means the photoresistor powers a small heater during the day and at night the heater is not powered and it is the heater that opens or closes the circuit to the light. So would the ETS be VL-T-E or VL-E-T-E or something else, maybe VL-E-T-M-E?

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Re: Energy Transfers

Postby wlmeng11 » December 25th, 2014, 9:54 pm

Thanks. A Wikipedia article says concerning a street light, "The photoresistor....controls whether current flows through the heater which opens the main power contacts. At night, the heater cools, closing the power contacts, energizing the street light." I am guessing this means the photoresistor powers a small heater during the day and at night the heater is not powered and it is the heater that opens or closes the circuit to the light. So would the ETS be VL-T-E or VL-E-T-E or something else, maybe VL-E-T-M-E?
If the thermal sensor and switch for the light are solid-state (eg. thermistor or thermocouple w/ power transistor driving the lights), then it would be VL-E-T-E for photoresistor to electric heater to thermistor/thermocouple to transistor. However, given the high power requirements of the street light, they may have to use a mechanical switch which could be activated via thermal expansion (eg. bimetallic strip). In that case, it would be VL-E-T-M-E for photoresistor to electric heater to bimetallic strip actuating a switch.

There are countless ways to design an automatic street light, so the only way to find out what energy transfers are involved is by looking at all the specific components inside :)
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Re: Energy Transfers

Postby goodcheer » December 27th, 2014, 6:54 am

Thanks. A Wikipedia article says concerning a street light, "The photoresistor....controls whether current flows through the heater which opens the main power contacts. At night, the heater cools, closing the power contacts, energizing the street light." I am guessing this means the photoresistor powers a small heater during the day and at night the heater is not powered and it is the heater that opens or closes the circuit to the light. So would the ETS be VL-T-E or VL-E-T-E or something else, maybe VL-E-T-M-E?
If the thermal sensor and switch for the light are solid-state (eg. thermistor or thermocouple w/ power transistor driving the lights), then it would be VL-E-T-E for photoresistor to electric heater to thermistor/thermocouple to transistor. However, given the high power requirements of the street light, they may have to use a mechanical switch which could be activated via thermal expansion (eg. bimetallic strip). In that case, it would be VL-E-T-M-E for photoresistor to electric heater to bimetallic strip actuating a switch.

There are countless ways to design an automatic street light, so the only way to find out what energy transfers are involved is by looking at all the specific components inside :)
Thank you. These concepts are truly inspiring. Maybe we will see some really unique ETSs for this event.

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Re: Energy Transfers

Postby SWAnG » December 27th, 2014, 12:41 pm

Wait so would conducting electricity through salt water count as e-c-e?

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Re: Energy Transfers

Postby A Person » December 27th, 2014, 7:39 pm

Wait so would conducting electricity through salt water count as e-c-e?
I wouldn't say so. You're not really transferring the energy. However, I would say that, for example, tipping a jar of salt(m) into water to make saltwater(c) which then conducts electricity(e) works. I think this would be in the same thought as using a switch to turn on a circuit.
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Re: Energy Transfers

Postby SWAnG » December 28th, 2014, 12:09 pm

hmm but are you not transfering the electrical current into the electrolyte solution (chemical) then back into the circuit?


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