Modelling current flow in a series circuit: get whole group to sit in a big loop. Everyone sits on one hand - pass round some cell holders/cells/balls. Once everyone bar one has one state that you want to pass a different cell/ball/whatever around the circuit - this makes it easy to spot. To pass the new ball anti-clockwise the gap will need to move clockwise.
Modelling current flow in a series circuit: get whole group to sit in a big loop. Everyone sits on one hand - pass round some cell holders/cells/balls. Once everyone bar one has one state that you want to pass a different cell/ball/whatever around the circuit - this makes it easy to spot. To pass the new ball anti-clockwise the gap will need to move clockwise. It gets everyone involved and they have to be paying attention. It works well with Y7 and I have done it with Y4. It makes a good starting point for how good models are. Discuss the good and bad points of the model while the different cell is moving around.
To ensure they understand why a bulb lights straight away when the switch is closed (as electrons move very slowly) get the kids to do the conga holding each other's waists, the contact represents the mutual repulsion of electrons that makes the battery light instantaneously.
Making the National Grid in the class room. You need a LOT of wires for this one (I used 1 box of wires between 5-6 kids. Ask them all to form one group which represents a city. Make a GIANT series circuit. Also have a normal circuit in the front with the same number of bulbs as the number of cities. Get them to think about why their bulbs are dimmer then the normal circuit. Should link to resistance. Then ask them to look at the circuits again and turn the knob to A/C. This makes the bulb go brighter and demonstrates the advantages of A/C current as opposed to D/C.