Unit ELECTROMAGNETIC INDUCTION AND ALTERNATING CURRENT The instantaneous value of sinusoidal alternating current is given by the equation sin t or sin ω θ (where θ = ωt ) whose graphical representation is given in Figure . . The sum of all currents over a half-cycle is given by area of positive half-cycle (or negative half-cycle). Therefore, I av = Areaof positive half-cycle (or negative half-cycle Ba selengthof half-cycle ( .
) Figure . Sine wave of an alternating current d Consider an elementary strip of thickness dθ in the positive half-cycle of the current wave (Figure . ). Let i be the mid-ordinate of that strip.
Area of the elementary strip = i dθ Area of positive half-cycle