1) Membrane walls of living cells have surprisingly large electric fields across

Question

1) Membrane walls of living cells have surprisingly large electric fields across them due to separation of ions. What is the voltage across an8.67-nm-thick membrane if the electric field strength across it is 9.06 MV/m? You may assume a uniform E-field.

2)   Two parallel conducting plates are separated by a distance d = 12.0 cm. Plate B, which is at a higher potential has a value of 620 V. The potential at x = 7.50 cm from the plate B is 64.1 V. See diagram below.

(a) What is the potential of plate A?

_______ V

(b) What is the direction of the electric field lines between the plates?

3)   A large capacitance of 1.01 mF is needed for a certain application.

(a) Calculate the area the parallel plates of such a capacitor must have if they are separated by 4.11 µm of Teflon, which has a dielectric constant of 2.1.

______m^2

(b) What is the maximum voltage that can be applied if the dielectric strength for Teflon is

60 106 V/m

__________ V

(c) Find the maximum charge that can be stored

_______ C

(d) Calculate the volume of Teflon alone in the capacitor.

__________ m^3

4) Find the total capacitance of the combination of capacitors shown in the figure below. (C1 = 2.52 µF, C2 = 21.7 µF.)

Explanation / Answer

1)

Here ,

thickness , t = 8.67 nm

t = 8.67 *10^-9 m

Electric field , E = 9.06 *10^6 V/m

Now , Voltage potential = E*t

Voltage potential = 9.06 *10^6 * 8.67 *10^-9

Voltage potential = 0.0785 V

the Voltage potential across the membrane is 0.0785 V

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