# Physics

posted by Stesson

Oscilloscopes have parallel metal plates inside them to deflect the electron beam. These plates are called the deflecting plates. Typically, they are squares 3.0 cm on a side and separated by 5.0 mm, with very thin air in between. What is the capacitance of these deflecting plates and hence of the oscilloscope?
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Using C = epsilon*area / distance:
C = (8.854e-12)(3e-2)^2 / (5e-3)
C = 1.59372e-12 or 1.6e-12
but this isn't correct.
Am I missing something? This is the only capacitance equation that uses area and distance.

1. Scott

the deflection is vertical AND horizontal
... two sets of plates

the "thin air" in the question is basically vacuum ... check your epsilon value

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