ELECTRICAL ENGINEERING

When two or more  inductors  are connected in such a way that same current flows through them, then it is said that they are connected in series. Like series connection of  resistors , series connected inductors can be replaced by an equivalent inductor. Let us assume that ‘n’ inductors having inductance of L 1 , L 2 , L 3 ,…L n  Henry are connected in series as shown in figure below. Since same current I is flowing through each of the inductors therefore voltage drop across inductors L 1 , L 2 , L 3 , …..L n  will be L 1 di/dt, L 2 di/dt, L 3 di/dt, …..L n di/dt respectively. Therefore from Kirchhof’s voltage law, V = L 1 di/dt + L 2 di/dt + L 3 di/dt + ……..+ L n di/dt     = di/dt (L 1  + L 2  + L 3  +…….+L n )  …………….(1) If the series connected inductors are replace by a single equivalent inductor Le then V = L e di/dt  …………………….(2) Comparing equation (1) and (2) we get, L e  = L 1  + L 2 ...

When the potential difference between the terminals of two or more  inductors  are same, it is said that they are connected in parallel. As potential difference or voltage across the terminals are same therefore current flowing through the inductors may or may not be same. If the parallel connected inductors have the same value of inductance then equal  current  will flow through them. If the value of inductance are not same then current through the inductors will be different. Equivalent Inductance without Magnetic Coupling between  Inductors Consider the figure below. In the figure n inductors having inductance of L 1 , L 2 ,…..,L n  are connected in parallel and a voltage V is applied. Let current I 1 , I 2 ,….I n  is flowing through the inductors L 1 , L 2 ,……L n . The emf generated in the inductance will oppose the cause i.e. current flowing through the inductor as per  Lenz’s Law . Therefore, V = L 1 di1/dt = L 2 di2/dt = ………=L...