from what i've learnt, this is linear voltage regulator configuration. please check if i got the power dissipation calculation right.
to regulate at 3V output/load voltage from 12V input supply, we need 3.7V at the transistor's base, assuming hFe so high that Ib is negligible. so..
power dissipated by load (3ohm) = 3W
power dissipated in transistor = 9W
total = 12W (12V x 1A)
regardless of voltage regulation, the power dissipation is constant at 12W? (assuming the Rload is changable to be equal to Ve, say 3Ve = 3ohm, 1Ve = 1ohm, ie constant 1A through the load). the lower the output voltage, the greater the loss from the transistor? in other word, the lesser the output voltage, the more heat generated by the transistor?