okay so this is a quick one about potential difference in series circuits this is a series circuit it's a simple Loop the components just come one after each other um now to think about the potential difference in a series circuit we just need to remember what what what the current does in that circuit so the current is made up of electrons and the electrons flow around the CC CC uh you can imagine them gaining energy when they go through the cells and then giving up that energy to the components in the circuit so in this case electrical energy in the cells is going to be transferred to light and heat at the bulbs now uh potential difference is all about energy transfer potential difference the pot difference across a point in the circuit tells you how much energy is transferred to or from a CO of charge between those two points um now a of charge isn't the same as one electron as I've said before um a coolum of charge is actually a whole load of electrons millions of them um so we'll imagine a coolum of charge flowing around this circuit now as the coolum of charge goes through the cells the potential difference across those cells in total is 4 volts so this Kum of charge is going to get four jewles of energy and it has to give that energy up as it goes around the circuit now if each of these two bulbs are identical then it's going to give up an equal amount of energy to each of the two bulbs so if the potential difference across the first bulb measured with this voltmeter V1 is 2 volts the second one is also going to be 2 Vols and you'll notice that this adds up to the potential difference across the supply this is because the energy from the supply is being divided up between the two bulbs so the potential difference across the two components adds up to the potential difference of the supply now we could replace this circuit with a slightly different circuit which doesn't contain two identical components so this circuit contains a bulb and a motor which are completely different from each other now as the charge flows around this series circuit picks up energy at the cells and shares that energy out between the components now it turns out in this example that the potential difference across the bulb is only one VT that means of the four jewles of energy this coolum of charge picks up at the cells only one Jewel of energy goes to the bulb therefore how many how many jewels of energy go to the motor it must be 3 jewles what's the potential difference across the motor it must be 3 Vol so in a series circuit energy is divided energy is shared between the components in that series circuit therefore the potential difference of the supply is shared out between the components in that series circuit but the potential difference across all the components in series adds up to the potential difference of the supply that's because the energy shared between all the components in Series has to add up to the energy given out by the supply