Question

A boy rubs a neutral glass rod with a neutral silk cloth and observes that the silk cloth becomes negatively charged by friction. Then which of the following is true about the glass rod?
1. The glass rod remains neutral
2. The glass rod became negatively charged.
3. The glass rod became positively charged
4. None of the above

Answer 1

Correct Answer - Option 3 : The glass rod became positively charged

The correct answer is option 3) i.e. The glass rod became positively charged

CONCEPT:

​Object acquire charge by three methods:

• ​Charging by friction: When two objects are rubbed, due to friction there occurs a charge transfer. 
  • An object loses its electrons, while the other object gains electrons.
  • The object that loses electrons becomes positively charged and the object that gains electrons becomes negatively charged.
• Charging by conduction: In this method, a charged conductor is brought in contact with another neutral body.
  • The neutral body acquires a charge such that the measure of charge on the neutral and charged conductor is the same.
• Charging by induction: This method is used to charge an object without actually touching the charged object.
  • The charged object is brought near the uncharged object. The end of the uncharged object near the charged object develops a charge of the opposite polarity. 

EXPLANATION:

• Rubbing a glass rod with a silk cloth causes friction.
• If the silk cloth becomes negatively charged by friction, it means that the electrons transferred from the glass rod to the silk cloth.
• As the glass rod loses electrons, it has an excess of a positive charge.
• Hence, the glass rod will become positively charged.