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A stationary,circular wall clock has a face with a radius of 15cm Six turns ofwire are wound arout its permeter the wire carries a current 2.0A in the clockwise direaction The clcok is located where there is a contant, uniform external magnetic filed of 70m T (but the clock still keeps perfect time) at exactly 1 :00p m the hour hand of the clock points in the direction of the external magnetic field (a) After how many minutes will the minute hand point in the direction of the torque on the winding due to the magngetic field (b) What is the magnitude of this torque . |
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Answer» (a) After 20 minutes (b) `tau_(3) = NIAB sin 90^(@) = 6 xx 2 pi xx (0.15)^(2) xx 70 xx 10^(-)` `tau = 12 xx (22)/(7) xx 225 xx 70 xx 10^(-7) N -m = 5.94 xx 10^(-2) N -m`  .
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