Consider the following system - A coil is wrapped around a soft iron core as shown below. A permanent magnet is placed at one end of the coil. Code (Text): [FONT="Courier New"] +--+-----+--+ | | | | Coil +ve Side --> | | | | --> Coil -ve Side | | | | +--+-----+--+ +-----+ | | --> Permanent Magnet +-----+ [/FONT] Consider the magnet being moved from right of the screen (initial position) to the left of the screen. As the magnet moves towards the perfect alignment with the core (lets call it center), the flux linkage of the coil increases. -- Since there is a rate of change of flux linkage, I have voltage induced in the coil -- Assuming the circuit to be complete, I get a current flowing through the coil whose value is current = flux linkage / coil inductance As the magnet moves away from the center, the flux linkage decreases. However the magnitude of flux linkage is positive -- From the previous equation, current is still positive since flux linkage is positive -- Since the rate of change of flux linkage is negative, voltage polarity is reversed In the former case if I had assumed the polarity to be +ve, I have a situation where I get -ve voltage and + current Is this the reason why we say in an inductor current lags the voltage? If to close the circuit I had a simple resistor then how do I explain the presence of -ve power in this case? I do not know how to account for the negative power. Can someone please explain this to me.