The instructor pilot aboard a C172 landed without a clearance after suffering a total electrical system failure.

Narrative

I was five miles north of the airport on a training flight with a student. I was the instructor. I called the Tower for clearance back in to land. Upon initial contact; my radios began to flicker and I was unable to contact Tower. I tried for several minutes with no answer. I was also unable to talk to my student; and the radios kept switching to 121.5. Neither radio worked. I tried COM1 and COM2. Eventually the radios failed completely and I was unable to turn them on. The ELT then sounded and the alarm was going off loudly for the remainder of the flight. I squawked 7600 and had full VFR conditions so I climbed up to 4;000 MSL to get a visual of the airport to look for traffic and hoping to get a light gun signal. Upon reaching midfield; the remainder of the electrical system failed; the flaps would not work and I started to smell burning from the aircraft. With a full electrical failure and smoke and burning; I squawked 7700 and made an emergency landing without a landing clearance from Tower. I was afraid we were on fire. I made sure there was no aircraft in the area and the landing was completed without incidence. After landing I exited the runway and received light gun clearance to taxi in so I taxied to the ramp. I immediately called Tower and explained what had happened. I explained that I had an electrical failure and flight control failure. On final approach; the flaps had uncommanded oscillations up and down making the aircraft difficult to control. Tower said they were unable to pick up the transponder squawking 7600 or 7700.