1. The problem statement, all variables and given/known data 1) The coil of a moving-coil loudspeaker has a mean diameter of 30mm and is wound with 800 turns.It is situated in a radial magnetic field of 0.5T. Calculate the force on the coil, in newtons, when the current is 12mA. 2)Explain what happens when a long straight conductor is moved through a uniform magnetic dirld at constant velocity.Assume that the conductor moves perpendicularly to the field.If the ends of the conductor are connected together through an ammeter, what will happen? 3)A copper disc,250mm in diameter, is rotated at and prependicular to its plane. If the axis points magnetic north and south, calculate the e.m.f between the circumference of the disc and the axis. Assume the horizontal component of the earth's field to be 18uT. 2. Relevant equations 3. The attempt at a solution i don't know how to calculate the above questions.but i try to solve Q2 as the follow,please give me some advice and solution,thanks Q2 ans. A deflection was obtained on ammeter,when the direction of moving of conductor was reversed,ammeter was also deflected in the reversed direction.