Physics Electromagnetic Induction Level: High School
One method of measuring the magnetic field strength uses a closely-wound coil of wire N turns and enclosing an area A . This coil is initially placed so that the flux ¥õ through the area is a maximum (see figure at ¡°click here¡±) .Then in a small time interval . Delta t is rotated ¨ù of a turn so that it is parallel to the magnetic field , and the flux through its area reduces to zero .a) Two leads from either end of the coil are connected to a machine that measures the amount of charge Q (Q = I delta f) if the total resistance of the coil and the charge measuring device is R , derive an equation for the charge Q in terms of N,A,R and the negative flux density B .
b) A closely wound coil containing 200 turns is 45 cm in radius and has a resistance of 60.0 ohm . It is placed in a magnetic field . and connected to a charge-measuring instrument . The coil is initially perpendicular with the magnetic field , and is quickly rotated by ¨ù turn so that it becomes aligned with the field ,and a charge of 45.7 micro C is measured . What is the magnetic flux density of the field ?
