# relative permittivity and relative permeability of water - RF Cafe Forums

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elia_lyza
 Post subject: relative permittivity and relative permeability of water Posted: Mon Jan 05, 2009 5:49 am
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Do anybody knows the relative permeability and relative permittivity for water?

nubbage
 Post subject: Posted: Wed Jan 07, 2009 12:10 pm
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Location: London UK

Hi ella_lyza

Try this url.

The complex permittivity data given is good if the water is pure, but if mixed with other complex molecules, the value drops rapidly according to the relative mixture %.

Water is paramagnetic, but probably has a very low value ie close to 1.0

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nubbage
 Post subject: Posted: Wed Jan 07, 2009 12:21 pm
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Location: London UK

Further data:

at X band these figures are very reliable, coming from Institute of Physics, where the data was claimed to be accurate to within 0.2%. I quote:

It is found that epsilon '=62.256(37), epsilon "=31.570(47) at f=9.346 GHz, T=293K; and epsilon '=64.156(38), epsilon "=28.623(43) at f=9.370 GHz, T=298K.

My comment:

Note that over a small frequency range (9.34 to 9.37GHz) the value changes by about 4%, which I find rather surprising.

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nubbage
 Post subject: Posted: Wed Jan 07, 2009 12:28 pm
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Joined: Fri Feb 17, 2006 12:07 pm

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Even further data, applicable to water at 20* C and at F=2.45GHz can be found at

This shows epsilon' as 78 and epsilon" as 6.8

Google is a great tool for this sort of question.

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Posted  11/12/2012