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A wire PQ of mass 10 g is at on tow parallel horizontal metal rails. The spearation between the rails is 4.9 cm A magnetic field of 0.80 tesla is applied perpendicular to the plane of the rails, directed inwards . The resistance of the circuit is slowly decreased . When the resistance decreases to below 20 ohm, the wire PQ begins to slide on the rails. Calculate the coefficient of friction between the wire and the rails |
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Answer» Solution :Wire PQ begins to slide When magnetic force is just EQUAL to the force of friction, i.e ., `mu mg = il B sin theta (theta=90^0)` Here, `i = (E)/(R) = 6/20 = 0.3 A, ` `mu= (ilB)/(mg) = ((0.3)XX(4.9 xx 10^(-2))(0.8))/((10xx 10^(-3))(9.8)) = 0.12` |
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