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Electric Field Shapes
Electric fields are often represented by electric lines of force.  
   
A line of force is a line showing the direction of the force acting on a small positive charge placed in the field.  
   
The "density" of the lines represents the magnitude of the field strength.  
   
To draw a diagram showing the shape of an electric field, imagine a small positive charge (a test charge) to be placed in the field at different points.  
You can usually make some guesses as to the approximate magnitude of the force too, so you can draw arrows of appropriate lengths.  
   
Force due to a Single Point Positive Charge  
Wherever the test charge (represented by the red dot) is placed, the force will be directed away from the charge (or towards the charge if it is negative).  
   
Therefore, in this case, the shape of the field is radial as shown below.  
   
   
Field Due to Two Opposite Point Charges of Equal Magnitude  
In this slightly more complicated case, a vector addition is needed to predict the direction of the line of force at the point considered.  
However, we can still make some reasonable approximations as stated above.  
   
By considering a number of such additions, we obtain the following shape  
   
and, using the same ideas we can predict that the shape of the field in the vicinity of two similar charges of equal magnitude would be as shown in the next diagram.  
   
Notice that, at the centre of this field, there is a place where the magnitude of the electric field strength is zero.  
This is called a neutral point.  
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