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three wires are connected by thick copper wires with the six 
binding screws AB,CD,EF. 
On a concentric circle of twice the radius is arranged a 
coil of the same wire going twice round the circle and having 
its ends connected by thick wires with the binding screws 
GH. On the same circle is a single wire of twice the 
diameter, making only one turn round the circle, and having 
its ends connected with the binding screws KL. 
The coils are denoted respectively by the numbers 1 — 5. 
The null method is adopted in each case. That is two 
forces acting on the needle and arising from different 
