An electrochemical impulse traveling along the cell modeled in the figure (Figur

Question

An electrochemical impulse traveling along the cell modeled in the figure (Figure 1) changes the value of emf E3 so that now it supplies an upward current of40 nA . All resistors have the same value R = 1.0 M and E1=75mV, E2=45mV.

Part A

What is the value of E3?

Express your answer using two significant figures.

Figure 1 of 1

An electrochemical impulse traveling along the cell modeled in the figure (Figure 1) changes the value of emf E3 so that now it supplies an upward current of40 nA . All resistors have the same value R = 1.0 M and E1=75mV, E2=45mV.

Part A

What is the value of E3?

Express your answer using two significant figures.

Figure 1 of 1

Explanation / Answer

R = 1.0 M
E1= 75mV,
E2= 45mV
E3 = ?
Current I = 40 nA
Current in E1 = I1
Current in E2 = I2

I = I1 + I2 -----------1

Now,
R*I + R*I2 + R*I + E2 = E3
2R*I + R*I2 = E3 - E2
2*1*10^6 * 40 * 10^-9 + 10^6 * I2 = E3 - 45 * 10^-3
0.08 + 10^6 * I2 = E3 - 45 * 10^-3 --------2

R*I + R*I1 + E1 + R*I1 + R*I = E3
2R*I + 2R*I1 = E3 - E1
2*1*10^6 * 40 * 10^-9 + 2*10^6 * I1 = E3 - 75 * 10^-3
0.08 + 2*10^6 * I1 =  E3 - 75 * 10^-3   ---------3

Using Eq 1 , Eq 2 & Eq3

E3 = 161.7 mV

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