Definition of the ampere: |
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Sincel is perpendicular to B2, the magnitude of F1 is |
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We can rewrite this in terms of the force per unit length as |
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The numerical value of 2x10-7 N/m is obtained from the equation above with I1= I2= 1 A and a = 1 m. The Ampère's law states that the line integral of B.ds around any closed path equals |
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Ampère's law is valid only for steady currents and is useful only for calculating the magnetic field of current configurations having a high degree of symmetry. |