Fleming’* left-hand rule is a method to determine the direction of force acting on the conductor that is kept in a uniform magnetic field. It is not a process to determine the magnitude of the force but the direction of any of the three parameters; current, magnetic field and the force when the direction of two of the three parameters are known.
It states “Hold your thumb, the forefinger and the second finger at a right angle to each other. If the forefinger represents the direction of the field and the second finger represents that of the current then thumb gives the direction of the force”
