From an early age we are all taught to have a healthy respect for a different form of electricity in the home, namely current electricity. The batteries we use in our experiments with direct current circuits create very little power, and are harmless. However, the power supplied by the electric power companies can produce electric currents that can be lethal. The electrons in the copper plate are very mobile and move from the copper to your hand. On the other hand, the aluminum draws electrons from your hand.
Voltage is required to create a current.
Although your body is a very good conductor of electricity, it does offer some resistance to the flow of current, with the greatest resistance located in the skin. Dry skin is a very poor conductor of electricity. If you flipped the battery back and forth changing polarity very rapidly in the circuits you built above, you would create current in the circuit that would reverse direction each time you reversed the polarity of the battery in the battery holder. This of course is not a very practical way to create alternating current electricity. The amount of current an appliance draws depends on the ability of an appliance to resist electricity.