It gets heavier and heavier
The formula for energy of motion is KE = .5 x m x v^2
Ke= Kinetic Energy in Joules
m = Mass in Kilograms
v = Velocity in Meters per Second
The viscosity of magma is directly related to the silica content. That being said, the viscosity of magma is higher when the silica content is also high and it is a low viscosity magma when the silica content is also low. The silica content of low viscosity magma is approximately 45 - 55 wt%.
Electricity is the controlled flow of electrons. They are made to travel in the same direction at the same time. If you have an insulator, it stops or severely inhibits the flow of electrons. Such a device is found on telephone poles. Those are made of glass like materials.