The equation gives the dynamic relation between {TAIL ~ the voltage U} at and the power P through a connection to {HEAD ~ the load} 
The equation gives the dynamic relation between { TAIL ~ the voltage U } at and the power P through a connection to { HEAD ~ the load }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD