What is charging a body by rubbing called?

Charging a body by rubbing is primarily known as frictional charging or triboelectric charging. This process is a fundamental method of generating static electricity by bringing two different materials into contact and causing them to rub against each other.

Understanding Frictional Charging

Frictional charging occurs when two distinct materials are rubbed together, leading to a transfer of electrons between their surfaces. This electron transfer results in a net electrical charge on both objects. It's a common phenomenon responsible for many everyday static electricity effects.

The Mechanism of Electron Transfer

When two materials are rubbed, the atoms on their surfaces come into very close contact. Due to differences in their atomic structures and electron affinities, one material has a stronger tendency to gain electrons, while the other has a greater tendency to lose them.

• Electrons are transferred from the material with a weaker hold on its electrons to the material with a stronger attraction for electrons.
• The material that gains electrons becomes negatively charged.
• The material that loses electrons becomes positively charged.

For example, consider rubbing rubber against animal fur. The atoms of rubber possess a much stronger attraction for electrons than the atoms of animal fur. As a result, the rubber effectively pulls electrons from the animal fur. This transfer leaves the rubber with an excess of electrons (negatively charged) and the animal fur with a deficit of electrons (positively charged), creating a charge imbalance in both objects.

Key Factors Influencing Frictional Charging

Several factors can influence the extent and direction of charge transfer during frictional charging:

• Nature of Materials: The specific materials involved are crucial. A triboelectric series ranks materials based on their tendency to gain or lose electrons. Materials far apart in the series will generate a greater charge when rubbed together.
• Surface Area and Pressure: A larger contact area and more vigorous rubbing can increase the number of electrons transferred, leading to a higher charge accumulation.
• Environmental Conditions: Humidity plays a significant role. High humidity allows moisture in the air to conduct away the accumulated static charge, reducing its effect. Dry conditions are ideal for static charge buildup.

Common Examples of Frictional Charging

Frictional charging is frequently observed in daily life:

• Balloon and Hair: Rubbing an inflated balloon on dry hair causes the hair to stand on end as electrons are transferred between the balloon and hair, making them oppositely charged and attracted to each other.
• Walking on Carpet: Scuffing your feet across a carpet, especially in dry conditions, can build up a static charge on your body, leading to a static shock when you touch a grounded object like a doorknob.
• Comb and Hair/Paper: A plastic comb run through dry hair can attract small pieces of paper or lint due to the charge acquired by the comb.

Applications and Implications

While static electricity can be a minor nuisance, frictional charging has both practical applications and important safety considerations:

• Industrial Applications:
  • Photocopying: Toner particles are given an electrostatic charge to adhere to charged areas of the drum.
  • Electrostatic Painting: Paint droplets are charged and attracted to the oppositely charged object being painted, ensuring even coating and reduced overspray.
  • Air Purifiers: Charged plates or filters attract dust and pollen particles that have been electrostatically charged.
• Safety Concerns:
  • In environments with flammable gases, vapors, or dust (e.g., fuel depots, grain elevators), static sparks from frictional charging can ignite the materials, leading to explosions. Proper grounding and anti-static measures are critical in such settings.
  • Damage to sensitive electronic components can occur if static electricity discharges through them.

Simplified Triboelectric Series Examples

The triboelectric series helps predict which material will become positive and which will become negative when rubbed together.