Objects can acquire electric charge through different methods. Two common methods are charging by friction and charging by induction.
Charging by Friction
- Occurs when two different materials are rubbed together, causing electrons to transfer from one object to the other.
- The object that loses electrons becomes positively charged, while the object that gains electrons becomes negatively charged.
- This method is common with insulating materials, where charges remain localized.
- Examples:
- Rubbing a plastic rod with wool transfers electrons to the rod, making it negatively charged.
- Rubbing a glass rod with silk transfers electrons away from the glass, making it positively charged.
- This process is responsible for static electricity buildup.
Charging by Induction
- Involves charging an object without direct contact with another charged object.
- A charged object is brought near (but does not touch) a neutral conductor. This causes redistribution of charges within the conductor due to electrostatic forces.
- One side becomes negatively charged, and the other becomes positively charged.
- If the conductor is then grounded, charges can enter or leave, and the object becomes permanently charged after the external charged object is removed.
- This method works only with conductors, where charges are free to move.
- Important: The induced charge is always opposite in sign to the charge of the nearby object.
Key Differences
| Property |
Friction |
Induction |
| Contact required? |
Yes |
No |
| Materials used |
Mainly insulators |
Conductors |
| Charge origin |
Transferred between objects |
Redistributed within the object |
| Type of charge |
Can be positive or negative depending on material |
Always opposite to nearby charged object |
Both methods are important in understanding how static electricity builds up and how charged objects can influence others without physical contact.
Written by Thenura Dilruk