How Does Cotton React to Static?

Atomic Structure and Ionization

• All matter is made up of atoms. At the centre of an atom is the positively charged nucleus, which contains positively charged protons and neutrally charged neutrons. Surrounding the nucleus are negatively charged electrons. Overall, atoms are neutrally charged because they have an equal number of protons and electrons, and the charges cancel each other out. Atoms can lose electrons in a process called ionization. Atoms that have lost electrons are called "cations" and are positively charged, because they have more protons than electrons.

Static Electricity

• Static electricity occurs when an object has an imbalance in the number of positive and negative charges -- when its atoms have lost or gained electrons -- and this causes the build up of electrical charges on the object's surface. When you rub two objects together, negatively charged electrons are transferred from one object to the other. The object which loses electrons becomes positively charged and the other object, which gains electrons, becomes negatively charged.

  The charge that builds up can be discharged by connecting the object to Earth with a conductor. When we touch a statically charged object, the charge is discharged through your body, giving you a static shock.

Cotton and Static Electricity

• Cotton is a naturally occurring fibre that is spun into thread to make fabrics. When cotton is rubbed against a plastic rod, electrons are transferred from the cotton to the plastic rod, causing the cotton and rod to become positively and negatively charged respectively.

  The cotton is attracted to the rod -- since opposite charges attract -- and like charges repel. The cotton will react by moving towards the rod when they are brought close together. If the cotton and the rod touch, the electrons are transferred from the rod back to the cotton and the static is discharged.

Static Electricity Experiments

• You can experiment with static electricity at home. Vigorously rub some cotton, such as a cotton furniture duster, against a plastic object, like a plastic spoon. Hold the cotton near the rod and observe how the cotton moves towards it. Touch the objects to discharge the static, and again hold the cotton near the rod to see how it does not move now that the static is gone. Experiment with other fabrics, such as wool and nylon, to see if the type of fabric alters how much the fabric moves to the rod and how easily each material gives up electrons to build a static charge.