Answer:
[tex]1.7\cdot 10^{15} V m^{-1} s^{-1}[/tex]
Explanation:
The electric field between the plates of a parallel-plate capacitor is given by
[tex]E=\frac{V}{d}[/tex] (1)
where
V is the potential difference across the capacitor
d is the separation between the plates
The potential difference can be written as
[tex]V=\frac{Q}{C}[/tex]
where
Q is the charge stored on the plates of the capacitor
C is the capacitance
So eq(1) becomes
[tex]E=\frac{Q}{Cd}[/tex] (2)
Also, the capacitance of a parallel-plate capacitor is
[tex]C=\frac{\epsilon_0 A}{d}[/tex]
where
[tex]\epsilon_0[/tex] is the vacuum permittivity
A is the area of the plates
Substituting into (2) we get
[tex]E=\frac{Q}{\epsilon_0 A}[/tex] (3)
Here we want to find the rate of change of the electric field inside the capacitor, so
[tex]\frac{dE}{dt}[/tex]
If we calculate the derivative of expression (3), we get
[tex]\frac{dE}{dt}=\frac{1}{\epsilon_0 A}\frac{dQ}{dt}[/tex]
However, [tex]\frac{dQ}{dt}[/tex] corresponds to the definition of current,
[tex]I=\frac{dQ}{dt}[/tex]
So we have
[tex]\frac{dE}{dt}=\frac{I}{\epsilon_0 A}[/tex]
In this problem we have
I = 3.9 A is the current
[tex]A=(0.0160 m)\cdot (0.0160 m)=2.56\cdot 10^{-4} m^2[/tex] is the area of the plates
Substituting,
[tex]\frac{dE}{dt}=\frac{3.9}{(8.85\cdot 10^{-12})(2.56\cdot 10^{-4})}=1.7\cdot 10^{15} V m^{-1} s^{-1}[/tex]
