81. ||| CALC a. Derive an expression for the magnetic field strength at distance d from the center of a straight wire of finite length [ that carries current I. b. Determine the field strength at the center of a current-carrying square loop having sides of length 2R. c. Compare your answer to part b to the field at the center of a circular loop of diameter 2R. Do so by computing the ratio Byguare/ Beircle- 81. MOIL a. And (L/2)2 + d2 V2Mol b. TR