A rectangular coil of wire having N turns consists of a width w. The coil is joined to one arm of a balance and is hanged among the poles of a magnet. The field is uniform and perpendicular to the plane of the coil. The system is first balanced if the current in the coil is zero. If the switch is closed and the coil carries a current I, a mass m should be added to the right side to balance the system.
i) Determine an expression for the magnitude of the magnetic field and find out its direction
ii) Explain why is the outcome independent of the vertical dimension of the coil?
iii) Assume that the coil consists of 50 turns and width of 5.0 cm. If the switch is closed, the coil carries a current of 0.3A and a mass of around 20 g should be added to the right side to balance the system. Find out the magnitude of the magnetic field?