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oxon88
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Homework Statement
A multi-plate variable capacitor has 4 pairs of plates. The plates, when closed, are separated in air by 0.01mm. A capacitance range of 10 - 400 pF is required
a) estimate the required radius, R of each plate.
b) The capacitor is set to the maximum of 400 pF and is charged to 10v throught a 50KΩ resistor. determine: i) the initial value of current flowing. ii) the time constant for the circuit.
Homework Equations
capacitance = εr ε0A(n-1) / d
Initial current = V/R
Time constant = R x C
The Attempt at a Solution
a) 400x10-12 = εr ε0A(8-1) / (1x10-5)
can anyone explain what these 2 values are? (εr & ε0) i think one is dialectric strength. which for air is 3MV m-1 ?
b)
i) 10V/50Kohm = 0.2mA
ii) (50x103) x (400x10-12) = 20 μs