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# Advice on lines of force from a positive charge

In some old text it is mentioned that 4π lines of force originate from each unit positive charge. Could someone comment on that statement in view of the fact that 4π is not an integer.

3 years, 4 months ago

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This must be a very old text! There is no limit on the number of field lines that emerge from a point charge. You can start from that point charge, and head out radially in any direction, and you will be following a field line. If there are two point charges, then you can still head out from one charge in any direction, and you will be able to follow a field line (which this time will be curved, ending at the other charge if they have oppositely signed charges). When drawing diagrams, however, we cannot draw all the lines (!), so we draw a selection, and the relative closeness or otherwise of the field lines indicates the relative strength of the field in different parts of the diagram. If there are more lines passing through a test area, the electric flux through that area is greater.

What the text is referring to is (probably) the fact that there is $$4\pi$$ of what is called solid angle around the point charge (describing the range of directions there are out from the point), and since the field is spherically symmmetric, you could get a picture of this by thinking that the field lines are uniformly distributed across the $$4\pi$$ of solid angle. If you imagined there was one field line per unit of solid angle, that would be $$4\pi$$ field lines. · 3 years, 3 months ago