The SI unit for current is the Ampere

PHYSICS · Multi-part · CBSE · Physics · Moving Charges and Magnetism · Moving Charges and Magnetism

Problem

The SI unit for current is the Ampere, or Amp. (1) How is an Amp defined? (2) Show that the definition of an Amp is consistent with the equation Fl=μ0I1I22πr,\frac{F}{l} = \mu_0 \frac{I_1 I_2}{2\pi r} , where Fl\frac{F}{l} is the force per unit length of the wires, μ0\mu_0 the permeability of free space ( μ0=4π×10−7 N A−2\mu_0 = 4\pi \times 10^{-7} \text{ N A}^{-2} ), I1I_1 and I2I_2 are the two currents, and rr is the distance between the two wires. (3) Calculate the force per unit length experienced by two conductors in a vacuum, each carrying a current of 1 A separated by a distance of 0.25 m. (4) If the direction of the currents in part i is the same, what will be the effect of the force between the two conductors? What if the currents are in opposite directions?

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