Ice cube in an old Micro-oven giving visible electric shocks

[soopo]

I put 1 litre of ice cube to the micro-oven which is age is about 30 years. The shape of the ice cube was a little bit circular. I set the power of the micro to the maximum. There were continuous white electric shocks inside the micro. The ice cube contained a little fish which contained some micro grams of mercury.

I do not understand why the given electric shocks happened. The micro-oven sends microwaves. Probably most of them is reflected back. Probably because of the circular shape of the object the microwaves condensed gaining a lot energy to one point, since the electric shocks were not all over the micro, but smootly at the regular intervals.

The micro-oven gets energy from the house where are a lot halo-noise in the system of electricity because of the current mercury lamps used widely in the given area. The input system of the machine was not designed to overcome the given noise.

The 90s micro-ovens have not caused me such a issue. It seems that the given micro-oven uses different frequency than the given ones, probably by accident. I would expect that the design of the current micro-ovens forwards the electric shocks to the body of the micro and not to the air.

1. Why was he electric shock formed in the micro-oven?
2. How do the new micro-ovens forward the energy condensation in one point inside the micro?

 

[soopo]

There is no grounding in the house so the electricity could not escape and it went to the air. Ok.

Probably, the micro-oven gives the given electric shock always with the full power. I do not want to test it.
Probably, the shape or nature of the object does not affect the formation of the electric shocks.

Are my assumptions right?