Asimple solar cell uses what is called a photovoltaic effect in a semiconductor to create charges that can do work. using what you know about what semiconductors look like in visible light, explain what you think the "photovoltaic "effect is and why are semiconductors used rather than insulators or metals?

Amixture of slurry and mud is to be pumped through a horizontal pipe of diameter 500 mm. the fluid behaves as a bingham plastic with a yield stress of 30 pa and viscosity 0.04 pa.s. describe the effects of the shear stress through a transverse section of the pipe by plotting the variation in shear stress and velocity profile: (i) just before the slurry starts to move (ii) as the slurry flows when the pressure gradient is double that in part (i)