Use a ripened citrus fruit -- lemons work particularly well -- but you can always use an orange, grapefruit or lime, if you prefer. Squeeze the fruit, or roll it around a table to soften it a little. This breaks down the fibers in the fruit, making it juicier.
Put your fruit on a small plate. Cut two six-inch strips of thin bare copper wire using a knife. You can get copper wire from an electrical supply store if you don't have any, or you can remove the outer plastic from regular wire using wire strippers. Speaker wire is fine.
Insert the end of one of the copper wire strips into the side of the fruit. Push it in about an inch or two using your fingers.
Wind about a half-inch of the second copper wire around the top of a three-inch steel nail. You can put a small strip of adhesive tape around the wire and nail to hold the wire in place.
Insert the pointed end of the steel nail into the opposite side of the fruit from where you inserted the copper wire. Push it in about one to two inches using your fingers.
Place the opposite end of one copper strip onto one of the terminals of a small flashlight bulb, using your finger to hold it in place. Place the opposite end of the other copper wire onto the other terminal on the flashlight bulb using another finger. There is usually one terminal on the base of the bulb and the other terminal is the metal holder on the side of the bulb. The bulb illuminates, although it may not be very bright, or last very long.
Cut an 18-inch strip of bare copper wire using a knife. Wind the wire tightly around a three-inch steel nail starting at the top of the nail and working down to about a quarter-inch to a half-inch from the bottom. Ensure you leave a few inches loose when you start winding the wire around the nail as you need to attach the end to a battery.
Continue to wind the wire tightly back up the nail until you get to the top, then wind it back down to the bottom as before. Make sure you leave a few inches loose so you can connect the wire to the battery.
Place one of the loose ends of wire onto one of the terminals on your small battery. Hold the wire in place using a strip of electrical tape. Place the other loose wire from the nail onto the other battery terminal and hold it in place using tape.
Put a few metal paper clips on a table. Move your nail toward the clips and you see them move and stick to the end of the nail. Remove one of the wires from the battery and the clips fall off. However, you will find the longer you leave the battery connected, the more magnetized the nail gets and after a while you can disconnect the battery and the nail remains a magnet.