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A2 Physics | Post your doubts here

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. A cobalt-60 source having a half-life of 5.27 years is calibrated and found to have an
activity of 3.50 × 105 Bq. The uncertainty in the calibration is ±2%.
Calculate the length of time, in days, after the calibration has been made, for the stated
activity of 3.50 × 105 Bq to have a maximum possible error of 10%.

Can anyone please help me solve this. Question 9 from may/june 09 . I have gone through the marking scheme but I didnt get it.
HELP!!
 
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Torque of the coil depends on the Force exerted on it and the distance between the opposite sides of the coil. For maximum torque, you need maximum force, and that can only be achieved in a magnetic field if maximum number of magnetic field lines cut through the coil. The maximum field lines will cut through the coil only when the coil lies parallel to the field lines. If the coil lies normal to the field lines, the field lines will pass through the empty space in the coil and there will be no force on the coil, let alone a turning effect.
 
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