Electric field across a parallel plate capacitor

AI Thread Summary
The electric field across a parallel plate capacitor can be described by two formulas depending on the circuit configuration. In a series circuit with a resistor, the electric field is given by E = (V - IR)/L while the capacitor is charging; once fully charged, it simplifies to E = V/L. If the resistor is in parallel with the capacitor, the electric field remains constant at E = V/L throughout. The key distinction lies in whether the resistor is in series or parallel with the capacitor, affecting the potential difference across it. Understanding these configurations is crucial for accurately calculating the electric field in capacitor circuits.
johnj7
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Hello,

If I had a potential source (V) , a resistor R, and a parallel plate capacitor,

would the Electric field across the capacitor become

E = (V - IR)/L

L = distance between capacitor

or would the electric field simply become E = V/L

??

thank you!
 
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How is the circuit set up? Your E = (V - IR)/L would be correct for a purely series circuit. But the current would be zero (or quickly become zero as the capacitor charges) so your second formula is then correct.
 
johnj7 said:
Hello,

If I had a potential source (V) , a resistor R, and a parallel plate capacitor,

would the Electric field across the capacitor become

E = (V - IR)/L

L = distance between capacitor

or would the electric field simply become E = V/L

That very much depends on whether the resistor is in series or in || with the capacitor doesn't it?
 
Ah ic, oh okay I understand now.

so if in series,
clearly initially it is

E = (V-IR) /L
but after the capacitor is fully charged then E = V/L

however if in parallel from the start then

E = V/L, always

would this be correct?
 
If the V, R and C are all in parallel then they all have the same potential V.
 
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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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