A parallel-plate air capacitor is made from two plates 0.200 msquare, spaced 0.700 cm apart. It is connected to a 140 V battery. Part A: What is the capacitance?
Part B: What is the charge on each plate?
Part C: What is the electric field between the plates?
Part D: What is the energy stored in the capacitor?
Part E: If the battery is disconnected and then the plates are pulled apart to a separation of 1.60 cm, what are the answers to parts A, B, C, and D?

Respuesta :

Answer:

A)2.53 × 10⁻¹² F

B) 350× 10⁻¹² C

C) 20,000V/m

D) 2.48 × 10⁻⁸J

E) 110.6 pF , 350 pC, 20,000V/m, 5.54 x 10⁻¹⁰ J

Explanation:

A) Given:

Area of the plates = A = 0.200 m²

Distance of separation of the plates = d = 0.007 m

Battery voltage = V = 140 V

Formula for Capacitance : C = ε₀ A/d

ε₀ = Permittivity of free space =  8.85×10⁻¹²    SI units

C = [tex]\frac{(8.85\times 10^{-12})(0.2)}{0.007}[/tex]

   =  2.53 × 10⁻¹² F    

B) Charge on each plate: q = C V= (2.53 × 10⁻¹²)(140)    

                                                       = 350 × 10⁻¹² C

C) Electric field between the plates = E = V/d

                                                                  = [tex]\frac{(140)}{0.007}[/tex]

                                                                    = 20000 V/m

D) Energy = 0.5 C V²

                = (0.5)(2.53 × 10⁻¹²)(140)²

                = 2.48 × 10⁻⁸ J

E)  When the battery is disconnected, the charge and electric field remain the same.

A) Since d = 0.0016 m now,

C = [tex]\frac{(8.85\times 10^{-12})(0.2)}{0.016}[/tex]

   = [tex]110.6\times 10^-12[/tex]

    = 110.6 pF

B) Charge = Q =[tex]350\times 10^-12[/tex]

C) E= 20,000V

D) Energy = [tex]0.5 \frac{Q^2}{C}[/tex]

                  = [tex]0.5 \frac{(350\times 10^-12)^2}{(110.6\times 10^-12)}[/tex]

                  = [tex]5.54\times 10^{-10}[/tex] J