How Is the Capacitance of a Parallel-Plate Air Capacitor Calculated?

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The capacitance of a parallel-plate air capacitor can be calculated using the formula C = ε₀(A/d), where A is the area of the plates, d is the separation distance, and ε₀ is the permittivity of free space. Given an area of 0.0070 m² and a separation of 0.030 mm, the capacitance can be derived. An electric field of 4.0 × 10⁶ V/m is also relevant for understanding the capacitor's behavior under voltage. Participants discuss the importance of knowing how to calculate both series and parallel configurations of capacitors. The conversation emphasizes starting with basic formulas and understanding the relationship between charge, voltage, and capacitance.
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Each plate of a parallel-plate air capacitor has an area of 0.0070 m2, and the separation of the plates
is 0.030 mm. An electric field of 4.0 × 106 V/m is present between the plates. The capacitance of the
capacitor, in pF, is closest to:?


The capacitive network shown is assembled with initially uncharged capacitors. A potential difference, Vab = +100 V, is
applied across the network. The switch S in the network is kept open throughout.
 

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Capacitance is electric energy per charge, you should be able to calculate the electric energy for a given charge setup so just put Q -Q on the capacitor and continue on from there.

As for the second it is just about knowing how to calculate parallel and series of capacitors. You should be able to prove these from the definition of capacitance.

If you have any problems try to start, post how far you got and I can give you more from there.
 
yes i need help to start! thank you
 
welcome to pf!

hi vegamontalvo! welcome to pf! :smile:

(try using the X2 icon just above the Reply box :wink:)
vegamontalvo said:
Each plate of a parallel-plate air capacitor has an area of 0.0070 m2, and the separation of the plates
is 0.030 mm. An electric field of 4.0 × 106 V/m is present between the plates. The capacitance of the
capacitor, in pF, is closest to:?

what formulas do you know relating E d A Q and C for a capacitor ? :smile:
Klockan3 said:
Capacitance is electric energy per charge …


no, capacitance = charge per voltage
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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