# Is it possible to make magnetic field or electromagnetic field,or lets say the signal, travel a further distance?

i have searched this but have received no results on what could happen and what can be done to allow this to happen.for example,if i want to make the magnetic field or an electromagnetic field or lets say signal travel a further distance, regardless of shortening the spread of the magnetic field/electromagnetic field.

Or,if i want the field to be shortened,regardless of directing it at only a place,a direction or even a spot. Also,to add on,what if i used inductors to try to achieve this.

For example,try to place the inductors in a certain way,for example,like placing a indutor sandwiched inbetween two inductors,and or applying different currents/voltages to the pair of inductors and the inductor sandwiched inbetween the pair,will it achieve the effect of making the field or lets say signal travel further. Or will it be possible?

To also add on,what if the example of the inductors stated above is placed inside a material that the field cannot pass through,and when the field is controlled inside,will it be possible to send a magnetic field or signal further,as its somehow and somewhat conpressed and directed in a way or another/in a few ways.

• Welcome to the site, but your question is confusing. To start with the manetic field is governed by magnetostatics, en.wikipedia.org/wiki/Magnetostatics the electromagnetic field by electrodynamics, the classical theory of light included in that, en.wikipedia.org/wiki/Classical_electromagnetism . Using Farraday's law you can see how far the magnetic field is measurable. Light, and other frequency electromagnetic fields are self contained waves moving with velocity c. – anna v Oct 29 '16 at 10:29
• @anna-v,in short,is there a way to make the electromagnetic field given off by an inductor travel futher,or electromagnetic wave to tavel further,other than giving more voltages.Or if i bend or compress the magnetic field given off by that inductor by sandwiching it between two inductors. – Yi Chin Oct 29 '16 at 10:37
• Are you thinking of wave guides ? en.wikipedia.org/wiki/Waveguide. If you are, then this article seems to deal what I am guessing are your points. – user108787 Oct 29 '16 at 10:59
• @CountTo10,so by using a wave guide,(which is similar to my method stated above),will it be possible to make the electromagnetic field(or wave) to travel futher than it original travel in air? – Yi Chin Oct 29 '16 at 11:07
• waveguides do what the name says: they guide the electromagnetic wave. An electromagnetic wave travels in straight lines from the source with velocity c, a wave guide shapes it and guides it to where one wants it to go. Like light fibers. – anna v Oct 29 '16 at 11:18

This is not a full answer, but rather a short summary on waveguides which will hopefully be of some use to you.

Or, if i want the field to be shortened,regardless of directing it at only a place,a direction or even a spot.

Your question seems to suggest you want to keep the power constant whilst covering the furthest (or shortest) distance. The idea behind waveguides is that you restrict the spread of the wave to one or two dimensions, and minimise energy loss.

Without the use of a waveguide, signals will drop off as they follow the 3 dimensional inverse power law. Waveguides are commonly found in microwave applications, (but have a much wider application) and the physical design of each type is dictated by the use to which they are to be put.

Waveguide Types Wikipedia

Slab waveguides confine energy to travel only in one dimension, fiber or channel waveguides for two dimensions. The frequency of the transmitted wave also dictates the shape of a waveguide: an optical fiber guiding high-frequency light will not guide microwaves of a much lower frequency. As a rule of thumb, the width of a waveguide needs to be of the same order of magnitude as the wavelength of the guided wave.

Image Source: Wikipedia Waveguides

Electric field $E_x$ component of the TE31 mode inside an x-band hollow metal waveguide.

Also,to add on,what if i used inductors to try to achieve this.

For this question, and a pretty comprehensive article on waveguides, I suggest you read the webpage I have linked to on this answer. You may not need anything else if a properly designed waveguide fulfills your needs.

I am sorry, but you need someone more experienced than I to answer questions on induction, as I do not have the background to answer you properly on this aspect.

• Thank you actually, don't get too much feedback. – user108787 Oct 30 '16 at 3:11

(This assumes you are talking about a signal through empty space). Far field power drops off by $1/r^2$ because we live in three dimensions. So all else being equal (bandwidth, power, ambient noise), directivity is the only answer. The only way to increase directivity is by increasing the volume of the emitter (assuming, of course, proper emitter design). For examples, A large parabolic dish is more directive than a smaller one, and a longer laser is more directive than a shorter one.

• To make a laser that produces a beam that stays collimated for a longer distance, make the aperture diameter larger, not the length of the cavity longer. – The Photon Oct 29 '16 at 17:26
• Both diameter and length contribute to collimation in a laser (assuming it all remains well tuned). But also note that a given increase in size yields diminishing returns as that length increases. Often, laser tubes are a lot longer than they are wide, for practical reasons. So increasing an already long length improves things a lot less than increasing a much smaller width. – Digiproc Oct 29 '16 at 17:54