Let's say I have a battery and a capacitor that is neutral. Now I connect the battery positive terminal to only one plate of the capacitor. From what I know, there is a potential difference between the terminal and the plate so there should be an electric field that causes some of the negative charges of the capacitor connected plate to move to the terminal (through a conducting wire) to reduce the potential difference to zero. This makes the connected capacitor plate to be positively charged which in turn causes the not connected plate to be negatively charged because there is an electric field between the plates that causes negative charges to gather in the not connected plate. Now after this happens I expect that there is a difference in potential between the plates of capacitor. But with a multimeter connected to the plates of the capacitor I can observe zero voltage. Why is that? What do I miss?
Electric Fields – Why Can’t Voltage Be Observed Between Two Capacitor Plates with One Connected to a Battery?
batteriescapacitanceelectric-fieldselectricityvoltage
Related Solutions
The net charge of any of those internally connected pairs of plates is always zero. That is, when you charge the capacitors, charge doesn't leave the wire between C and D, it only moves along it, and is held in place by the electric field of the adjacent plates. If a circuit is completed that allows charge to flow from D's negative plate to A's positive plate, the charges will move back to the right place, but the net charge of the 4 capacitors will always be the same.
Connecting the positive terminal of A will not allow charge to flow back from D, so nothing will happen. Similarly, connecting the wire between C and D won't make charge flow in or out of it, at least not in any way significant to the circuit. It only changes the reference for where we make our measurements from.
The man is like the battery,he needs to do work against electric field to accumulate charges on the upper plate because the charges that the plate already has will oppose further accumulation of charges
Source of the image : MIT OpenCourseWare
Best Answer
There is no potential difference because the connection of the positive battery terminal simply causes a redistribution of charge on both plates, but no net charge on either plate. That would require current in a complete circuit involving the other battery terminal.
The free electrons of the connected plate move towards the surface of the plate connected to the positive battery terminal. That, in turn, induces movement of free electrons on the non connected plate towards the surface nearest the connected plate. But the end result is the net charge on the two plates remains zero for a potential difference of zero between the plates.
See FIG 1 below.
Hope this helps.