Static Electricity and Electroscopes

Static Electricity

• Static electricity occurs when objects gain or lose electrons.
• When objects touch, electrons can transfer, resulting in either both objects becoming charged or one gaining charge and the other losing it.
• Electrostatic discharge is a transfer of charge where two objects have different charges.

Electroscopes

• Electroscopes are instruments used to detect electric charges.
• They work by using a metal rod to detect charge, and the deflection of a pointer (or leaves) indicates the magnitude of the charge.

Law of Electric Charge

• Like charges repel, and unlike charges attract.
• Charges on an object are typically balanced so the object appears neutral.

Induced Charge Separation

• A neutral object can have charges separated without direct contact with a charged object.
• If you bring a negatively charged object near a neutral object, electrons will be repelled to the opposite side of the neutral object creating a temporarily positive and negatively charged side of the object.

Applications of Static Electricity

• Electroscopes: Detect charge.
• Paint sprayers: Ensure the paint adheres to the object.
• Dusters: Attract dust to remove it.
• Precipitators: Trap pollutants during emissions.

Charging Objects

• Friction: Rubbing two objects together transfers electrons.
• Contact: Transferring electrons by direct contact.
• Induction: Charging an object using another charged object, inducing a charge of opposite polarity on the object.

Electrostatic Series

• A chart showing the tendency of materials to gain or lose electrons when rubbed together.
• Used to predict the charge developed on materials during friction.
• Example: Wool (with electrons) will give up electrons to silk (gaining electrons).

Static Cling and Winter

• Static cling is worse in winter due to the low humidity.
• Low humidity prevents the air from holding moisture, leading to an increase in static charge on objects.

Charging by Contact

• Transferring electrons by physical contact with a charged object.
• The object now has a similar charge as the charging object

Grounding

• Transferring excessive electrons to the earth.
• A method of eliminating a static charge.

Conductors and Insulators

• Conductors allow electrons to move freely.
• Insulators prevent electrons from moving freely, creating build-up of static electricity.

Charging by Induction

• Temporarily changing the charge distribution on a neutral object.
• A charged object is brought close to the neutral object, causing separation of charges without direct contact.

Permanent Charging by Induction

• Charging an object permanently by induction requires a third metal object and temporarily charges it.
• This object becomes permanently charged after momentarily transferring the charge in an induced object to oppositely charged object.

Electrical Discharge

• Flow of electrons from an object with excess electrons to an object with a deficiency.
• Occurs when the charge difference becomes very high leading to an electrical spark or discharge.

Lightning Rods

• Conductors that protect buildings from lightning strikes.
• The pointed structure rapidly discharges the built up excess charge.