# A capacitor stores a separation of charge. To separate the charges on a capacitor, you have to move charges against where the E field wants to push them (the oppositely charges on the two plates are attracted and want to move together), so charging takes work. That work becomes stored energy -- just like carrying water up a hill so that you can let it roll down at a later time and turn a generator. The total amount of energy stored in a capacitor is ½|Q||ΔV|. We'll use this to determine the amount of energy stored in a cell membrane.In discussion, we found that a cell membrane maintains a potential difference of about 70 mV (0.07 V) between the inside and outside of the membrane. We also found that a 1 μm by 1 μm section of the membrane has a capacitance of about 1.75  10-15 F. The radius of the cell is 10 μm.  4. What is the total energy stored in the full cell membrane? The answer is NOT 1.539e-13, 8.56e-18, or 4.28e-18.

Question

A capacitor stores a separation of charge. To separate the charges on a capacitor, you have to move charges against where the E field wants to push them (the oppositely charges on the two plates are attracted and want to move together), so charging takes work. That work becomes stored energy -- just like carrying water up a hill so that you can let it roll down at a later time and turn a generator. The total amount of energy stored in a capacitor is ½|Q||ΔV|. We'll use this to determine the amount of energy stored in a cell membrane.

In discussion, we found that a cell membrane maintains a potential difference of about 70 mV (0.07 V) between the inside and outside of the membrane. We also found that a 1 μm by 1 μm section of the membrane has a capacitance of about 1.75  10-15 F.

The radius of the cell is 10 μm.

4. What is the total energy stored in the full cell membrane?

The answer is NOT 1.539e-13, 8.56e-18, or 4.28e-18.