Design an activity to show like charges repel and unlike charges attract
Answers
Rub two inflated balloons with a woolen cloth, and hold the balloons together closely. They will try to spring apart.
Rub two pieces of nylon on a sheet of paper and then hold them together closely. Again, they will try to spring apart.
Now hold one balloon and one piece of nylon together closely. This time, the nylon clings to the balloon.
This is what has happened:
The two balloons have taken electrons from the woolen cloth and so have acquired a negative charge. The two pieces of nylon have lost electrons to the sheet of paper, and so have acquired a positive charge.
The experiment demonstrates one of the most important laws of electricity: like charges repel and unlike charge attract. The two negative charges (on the balloon) tried to push each other away. The two positive charges (on the piece of nylon) also tried to push each other away. But the unlike charges, the balloon and the nylon, tried to move closer together. You will see the importance of this law when we examine electric current and how electric current is produced. The word "static” means "at rest”, and static electricity is electric charges which are at rest in an object. If we can make these charges move in some way, we produce electric current.
or
A charged glass rod is suspended by a silk thread, such that it swings horizontally. Now another charged glass rod is brought near the end of the suspended glass rod. It is found that the ends of the two rods repel each other (Fig 1). However, if a charged ebonite rod is brought near the end of the suspended rod, the two rods attract each other (Fig 2). The above experiment shows that like charges repel and unlike charges attract each other.The property of attraction and repulsion between charged bodies have many applications such as electrostatic paint spraying. powder coating. fly-ash collection in chimneys. ink-jet printing and photostat copying (Xerox) etc.
Summary:
(i) If a glass rod is rubbed with a silk cloth, it acquires positive charge while the silk cloth acquires an equal amount of negative charge.
(ii) If an ebonite rod is rubbed with fur, it becomes negatively charged, while the fur acquires equal amount of positive charge. This classification of positive and negative charges was termed by American scientist, Benjamin Franklin.
Thus, charging a rod by rubbing does not create electricity, but simply transfers or redistributes the charges in a material.
