: The French mathematician Adrienne Marie discovered the law of the ball between two conductors carrying an ampere current. This formula is named after him. The force acting between two current-carrying parallel conductors is proportional to the length of the two conductors and the product of the current flowing between them is proportional and the distance between the two conductors is disproportionate. If the operating force is F, the current I1 and I2, the length of the two conductors is L, the distance between the two conductors is r , then , F α I1I2L / r or , F = 2X10-7I1I2L / r Here , 2X10-7 = proportional constant