Polystyrene has dielectric constant 2.6 and dielectric strength 2.0 × 107 V/m . A piece of polystyrene is used as a dielectric in a parallel-plate capacitor, filling the volume between the plates.

a- When the electric field between the plates is 77 % of the dielectric strength, what is the energy density of the stored energy?

Express your answer with the appropriate units

b- When the capacitor is connected to a battery with voltage 500.0 V , the electric field between the plates is 77 % of the dielectric strength. What is the area of each plate if the capacitor stores 0.25 mJ of energy under these conditions?

Express your answer with the appropriate units

Researchers conducted an experiment to identify the effects of three different hand sanitizers on the growth of bacteria. the researchers grew one type of bacteria in twenty-four identical covered petri dishes. then, they opened eighteen petri dishes and applied the three hand sanitizers to six petri dishes each. they left the remaining six petri dishes closed as a control group. when the researchers measured the growth of bacteria two days later, the six dishes that had no hand sanitizer showed the least amount of bacterial growth. the researchers concluded that not using any hand sanitizer would lead to the least bacterial growth. which statement best explains why the researchers’ conclusion was not justified? the experiment tested too many variables. the control group was not treated the same as the experimental group. the sample size of twenty-four petri dishes is not large enough. the single type of bacteria is not adequate to make any conclusions.