# Non-changing current with C-EMF

Discussion in 'General Electronics Discussion' started by XRZ, Jul 30, 2014.

1. ### Gryd3

4,098
875
Jun 25, 2014
If you account for the resistance in the power source, the actual current induced by the EMF is far lower than we are writing down. This would drastically reduce the power consumption you are concerned with.

2. ### XRZ

78
0
Jul 30, 2014
@Gryd3, could you use an example(need numbers to visualize!).

3. ### XRZ

78
0
Jul 30, 2014
Btw, what do all think of my suggestion to use a dc/dc converter? With a 300W input power to sustain 100A @3VDC? Does it make any sense?Could it work?

@Arouse1973 , @Gryd3

Last edited: Sep 19, 2014

4,098
875
Jun 25, 2014
5. ### XRZ

78
0
Jul 30, 2014
Making the issue of power negligible! Dropping the 10,000W required input significantly!
No need for 100V x 100A I guess !
Okay, it seems that it is indeed possible to solve such a problem, and not exhaust enormous power. I just wanted a solution where I can add more voltage to a system, without adding x100 or x1000 times of power. Like the example I proposed, where back-emf induced is 2V and the source voltage has to be 3V to maintain 100A, that should require a power source of 300W, but due to the resistance of the circuit the ideal input would be 100A @ 100VDC, but that's a lot more than what we need! So it does make sense to use other methods to reduce power.

Last edited: Sep 19, 2014
6. ### Gryd3

4,098
875
Jun 25, 2014
I think we're all on the same page... know there was something simple we were missing.

Thanks @Arouse1973 for filling the blank spot in my head!

7. ### XRZ

78
0
Jul 30, 2014
But, if you think about it a bit.. how much power do we actually need a factor of what ?
How can we calculate the power that's going to be exhausted additionally to maintain the same current when back-emf is induced by a magnetic field?

8. ### Gryd3

4,098
875
Jun 25, 2014
I think that would be way over my head. You would need to factor in the rate of change, and figure out what the equivalent resistance is of the circuit including the power supply to determine how much of a difference would actually be made.

5,165
1,087
Dec 18, 2013
Ok XRZ lets have a go. You need gives us some info. We need to know the size and length of the wire and current in the wire. We need to know what the EMF source is. Inductance, frequency, and voltage. Make it up if you have to but be reasonable. If not I can assume a few things. I cant do it right now as I am on my Tablet.

10. ### XRZ

78
0
Jul 30, 2014
Okay, consider it to be a copper square that is 20 cm wide, 0.4cm thick, 20 cm long. Its resistance is about 4.2x10^-5 Ω, inductance : 56 nH , magnetic field is a 0.5T uniform field from an electromagnet.
Voltage should be: 0.0000042Ω x 1000A = 0.0042VoltsDC. Imagine the magnetic field changing contniously(however you would like to imagine it going on/off or rotating next to conductor). However, the change is massive. delta(BA)/delta(t) = 0.5Tx0.4m^2/0.100s = -2VDC induced back-emf.

What is the factor of power jump here? From 0.0042VDC x 1000A = 4.2W to what...?

I hope this is a reasonable example, if you need to please adjust it! for frequency I dont know why it's needed since it's a DC circuit?

Last edited: Sep 19, 2014

5,165
1,087
Dec 18, 2013
Thats quite precise lol is this a question from a book?

12. ### XRZ

78
0
Jul 30, 2014
The intuitive power required to do this: (2.0042VDC)^2/(0.0000042Ω) = 956385W, That's 227710 times greater than the original input.

78
0
Jul 30, 2014

5,165
1,087
Dec 18, 2013
Yeah right.

15. ### XRZ

78
0
Jul 30, 2014
@Arouse1973 I really did... I've had this idea in my mind for a while now so...

5,165
1,087
Dec 18, 2013
Ok whats the project or is it secret?

17. ### XRZ

78
0
Jul 30, 2014
Its not a project at all...an experiment to prove the possibility of maintaining the same current on a conductor, without exhausting enormous power.
I self-teach myself electronics and tropics in electrical engineering on my own free time(oh and Physics!), and really tend to think of abstract experiments!
Which teaches me a lot of things, and sometimes conceptualize more.

18. ### XRZ

78
0
Jul 30, 2014
@Arouse1973 it seems that I caught your interest?
Btw, is what I'm proposing common... or I'm asking something weird...? Because I don't think this is a typical question/problem.

5,165
1,087
Dec 18, 2013
Thats good I am the same. I am not academic so my brain is free to think way outside the box at times. I love Physics also and how odd it can be at times

XRZ likes this.