In 0.20 s, a coil of wire with 50 loops experiences an average induced emf of 9.
ID: 2017932 • Letter: I
Question
In 0.20 s, a coil of wire with 50 loops experiences an average induced emf of 9.0 V due to a changing magnetic field perpendicular to the plane of the coil. The radius of the coil is 10 cm, and the initial strength of the magnetic field is 1.5 T. Assuming that the strength of the field decreased with time, ( a) what is the final strength of the field? ( b) If the field strength had, instead, increased, what would its final value have been? ( c) Explain a method whereby you could, in principle, tell whether the field was increasing or decreasing in magnitude.Explanation / Answer
induced emf = N (d /dt ) = NA (B/t) (a) B = Bf - Bi = t * /NA Bf = ( t * /NA ) + Bi ..................(1) Here N = number of loops = 50 = 9.0 V , t = 0.2s , A = r2 = ( 0.1)2 = 0.0314 m2 inirial magnetic field Bi = 1.5 T plug all values in equation (1) ,we get Final magnetic field Bf = 2.64 T (b) Field sterength is increased(c)Any induced electromotive force will be in the direction such that the magnetic flux it
creates will oppose the change in the flux that produced it.