Building your own battery. Demonstrate your battery to the class. Click here for directions. It can be likened to the flow of water through pipes and radiators, etc. As water is pushed through pipes by a pump, electric current is pushed through wires by a battery.
Hot water does work by heating radiators.
Electric current does work by heating fires, lighting lamps, ringing bells, electroplating, etc. A basic law of the universe is that like charges repel and unlike attract. Two negatives will repel each other. A negative and a positive will attract each other. An electron has a negative charge.