# Physics

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Consider a charging capacitor made out of two identical circular conducting plates of radius 21 cm. The plates are separated by a distance 8 mm (note that d<<a). The bottom plate carries a positive charge

Q(t)= Q0(1+t/T)
with Q0 = 5e-06 C and T = 0.005 sec, and the top plate carries a negative charge -Q(t). The current through the wire is in the positive k-direction. You may neglect all edge effects.

(a) Calculate the components of the electric field (in V/m) inside the capacitor for 2T?

(b) Calculate the components of the magnetic field B (in Teslas) at time 2T inside the capacitor at a distance 8.4 cm from the central axis of the capacitor.

(c) Calculate the components of the Poynting vector S (in W/m²) at time 2T between the plates at a distance r = 8.4 cm from the central axis of the capacitor.

(d) What is the flow of energy (in W) into the capacitor at time 2T ?

(e) How fast is the energy stored in the electric field changing (i.e. what is the rate of change in W) within the capacitor at time 2T ?

• Physics -

its a mystery

• E&M -

• Capacitors -

(a)
i)0
ii)0
iii)Q(t) = 3 * Q_0
and E = Q(t)/(A * epsilon_0)
....where A = pi*a^2
(b)
i)0
ii)don't know
iii)0
(c)
i)don't know
ii)0
iii)0
(d)
i)don't know
(e)
i)don't know

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