Added note on voltage source with resistance and how conductivity in added

docs/source/input_hash_cmds.rst

@@ -865,6 +865,10 @@ Allows you to introduce a voltage source at an electric field location. It can b
 
 For example, to specify a y directed voltage source with an internal resistance of 50 Ohms, an amplitude of five, and a 1.2 GHz centre frequency Gaussian waveform use: ``#waveform: gaussian 5 1.2e9 my_gauss_pulse`` and ``#voltage_source: y 0.05 0.05 0.05 50 my_gauss_pulse``.
 
+.. note::
+
+    * Where a resistive voltage source is placed at a location that is not free space, the conductivity (determined from the resistance) of the voltage source will be added to the underlying conductivity of the existing material at that location. For example, if a resistive voltage source of 50 Ohms is placed at a location where the material has a relative permittivity of 4 and conductivity of 0.1 S/m, the conductivity of that cell edge will become 0.12 S/m.
+
 #transmission_line:
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