# Electricity (Electric potential)

1. Aug 12, 2013

### marvelous

Hi,can you please help to understand why is the potential difference the same across the gap between the plates of both capacitors connected in parallel?

2. Aug 12, 2013

### Staff: Mentor

All points connected together by a thick copper wire are at the same voltage. The "top" terminal of one capacitor is connected by wire to the "top" terminal of the other, causing those terminals to be at the same voltage. The same goes for the "bottom" terminals of both capacitors. So the potential difference across one capacitor is going to be equal to the potential difference across the other.

3. Aug 12, 2013

### marvelous

So what if they were connected in series,how would the potential difference be affected?

4. Aug 12, 2013

### Crazymechanic

Cut in half , if you connect capacitors in series , say like two capacitors in series , you input say 120v DC you get 60 measuring from the "middle" to the ground.

5. Aug 12, 2013

### sophiecentaur

That will only be true if the two capacitors have the same value. The initial charge that flows will be equal for the two capacitors so the voltages will be Q/C, in each case. The value of the charge Q will be V(overall series Capacitance). i.e. the voltage is shared according to the inverse of the two capacitances. (Fewer volts across the larger capacitor)

6. Aug 12, 2013

### Crazymechanic

Thanks for pointing that out I totally forgot about that , well anyway it's the same as with resistors in series , change the one to a lower resistance and the other one closer to ground to a higher and you get more than half of the original volts you supplied do it the other way around and you get less than half , in both cases capacitor or resistor the thing is called a voltage divider.

7. Aug 13, 2013

### Staff: Mentor

For two capacitors in series, the sum of their individual voltages equals the applied voltage.