Inductive interference from two EM coils (aka a transformer)

AI Thread Summary
Transformers in electronic devices draw power even when turned off, as they consist of coils that create magnetic fields and heat. The source coil acts as an inductor, providing resistance and consuming power, regardless of whether the device is actively using electricity. The induced current in the secondary coil does not affect the power drawn from the source, suggesting that the device's off state does not eliminate energy consumption. Therefore, simply turning off a laptop may not significantly reduce power usage, as the transformer continues to draw power. This raises questions about the effectiveness of turning off devices to save energy.
borderLine
Messages
2
Reaction score
0
I've been wondering about this for a long time.

The little black box that you plug into the wall so you can power your electronic devices contains a general run-of-the-mill transformer.

But if the power is completely shut off to the device: not draining any current waiting for a power button to be pressed, or even unplugged from the device end so the cord is left dangling; then shouldn't the power consumption from the source (the power company's electric meter) be the same as if it were drawing the maximum that this device possibly could?

The source coil in the transformer is a simple inductor. It provides a load (resistance from the coil) which is converted to (marginal) heat and a magnetic field. The other coil induces an electric current (and a bit more heat) from the alternating magnetic field.

Whether or not that other coil uses that induced current shouldn't affect the current drained from the source, right? I mean the entire circuit of the device could be replaced with a theoretical metal plate representing the resistance of the entire circtuit (reactance and impedance not applying after AC->DC conversion takes place). Now, I don't see how drain to source inductance can make any printed circuit or conglomerate of wires or whatever induce a voltage in the source and stop the source coil from being a straight (-) ---v^v^--- (+) circuit. (that's a resitor)So there's really no point in turning my laptop computer off, right?
 
Last edited:
Science news on Phys.org
That doesn't help at all.
 
Thread 'A quartet of epi-illumination methods'
Well, it took almost 20 years (!!!), but I finally obtained a set of epi-phase microscope objectives (Zeiss). The principles of epi-phase contrast is nearly identical to transillumination phase contrast, but the phase ring is a 1/8 wave retarder rather than a 1/4 wave retarder (because with epi-illumination, the light passes through the ring twice). This method was popular only for a very short period of time before epi-DIC (differential interference contrast) became widely available. So...
I am currently undertaking a research internship where I am modelling the heating of silicon wafers with a 515 nm femtosecond laser. In order to increase the absorption of the laser into the oxide layer on top of the wafer it was suggested we use gold nanoparticles. I was tasked with modelling the optical properties of a 5nm gold nanoparticle, in particular the absorption cross section, using COMSOL Multiphysics. My model seems to be getting correct values for the absorption coefficient and...
Back
Top