After a plastic comb is used for straightening dry hair (or rubbed on wool) it becomes electrically charged. The charge creates an electric field which then induces charge separation in nearby paper bits thus leading to a net electrostatic attractive force between the bits and the comb.
Try the following
- Rub your feet on a carpet and touch a doorknob. What happens?
- On a cold dry morning,
have you ever felt that while removing a pullover, the hair on your hands stand
- Take a plastic comb and comb your hair quickly. (Your hair has to be dry). Take a few pieces of paper and hold the comb close to the papers. The papers will
tend to get attached to the comb.
- Instead of a comb, try the same experiment using
a glass rod. Rub the rod on a silk cloth, which will then get lifted towards the
The main basis of electricity and magnetism is the electric charge. The charges
tend to move so as to achieve an electrically neutral situation. Nature likes to
be electrically neutral. A charge creates a region of influence that we call electric
field. Charge, the electric field around it, and motion of charge, make up the entire
branch of electricity and magnetism. To understand the basic concepts of electric
charge, electric field and electric force, we will discuss very simple situations
where the charges are stationary or when they move, they do not disturb the electrical
Experiences of electric charges in our everyday lives:
One of the
best examples of observing effects of electric charges is lightning. It is one of
nature’s spectacular offerings. Moisture bearing clouds are initially electrically
neutral. But as the masses of clouds increase in size, they start rubbing against
each other. Friction makes electrons jump, so that between two clouds there will
be a charge imbalance - one cloud is positively charged and the second cloud is negatively
When a positively charged cloud collides with a negatively charged cloud,
charge neutralization occurs and sparks are produced. These sparks are seen as lightning.
Sometimes the charge imbalance can occur between a cloud and the earth; lightning
is seen when the charges are exchanged between the cloud and the earth.
What is making the paper stick to the comb or the glass rod? An easy interpretation
of these observations is that some objects when rubbed acquire a property that we
intuitively know to be charge. The paper piece also gets a charge imbalance due
to presence of charged comb or rod.