Magic of Science

Static electricity-induced polarity

 

 

 

A Van De Graaff Generator is used to generate static electricity. As the name implies the charge is static or stationary and builds up on the generator or what ever is attached to it.

 

 

 
A charged object can attract a neutral object by inducing a polarity on this neutral object, as shown in the animation on the right. Notice how the neutral object has an equal number of negative and positive charges. However, when the neutral object comes close to the positive charge its charge distribution becomes distorted. The positive charges in the neutral object are repelled while the negative charges are attracted closer to the nearby positive charged object.

 

Try these exercises. Charged balloons are used to induce a charge upon neutral metal cans. Identify the type of excess charge which would be present on cans labeled in the diagrams on the right. Keep in mind that metals have both positive and negative charges. However only negative charges, namely electrons, can move about.

a) Consider the first exercise. A positive charged balloon is brought close to two neutral metal cans as shown on the right. The cans are then separated.

i) What is the charge on can A?

ii) What is the charge on can B?

Solution

b) Consider the next exercise. A positive balloon is brought close to two cans from one side. A negative charged balloon is brought close to the cans on the other side, as shown on the right. The cans are then separated.


i) What is the charge on can A?

ii) What is the charge on can B?

Solution

c) Consider the third exercise. Two negative balloons are brought close to each end of a row of three cans as shown on the right. The cans are then separated.


i) What is the charge on can A?

ii) What is the charge on can B?

iii) What is the charge on can C?

Solution

Explain how strips of charged tissue paper are attracted towards a neutral object?

 

 

Play the video on the right to see the man made octopus come to life as it tries to grab onto the earthing rod.

Explain this phenomenon from what you know of induced polarity.