flip-flop:
flip-flop as (bistable, in the case of counters, registers and memory) multivibrator
http://www.eelab.usyd.edu.au/digital_tutorial/part2/flip-flop01.html
inductor:
changing current in an inductor produces an EMF in the inductor which opposes the current change...
-> reactance (ohms) whuch is the ac equivalent of resistance and in case of inductor is effected by frequency (high frequency high reactance)