Electric Charge: Definition, Types & Units

Electric Charge

• Electric charge is a property of matter that produces and experiences electrical and magnetic effects.

Types of Charges

• There are two types of charges in nature: positive and negative charges.
• Like charges repel each other, while opposite charges attract each other.

Unit and Dimensional Formula

• The SI unit of charge is the coulomb (C).
• 1 C = 10^6 μC, 1 μC = 10^(-6) C, 1 nC = 10^(-9) C.
• The CGS unit of charge is the esu, where 1 C = 3 × 10^9 esu.
• The dimensional formula for charge is [Q] = [AT].

Point Charge

• A point charge is a charge whose spatial size is negligible compared to other distances.
• Charge is a scalar quantity, meaning it can be added or subtracted algebraically.
• Charge is transferable and can be transferred from one body to another.
• Charge is always associated with mass, but mass can exist without charge.
• Charge is conserved, meaning it cannot be created or destroyed.
• The numerical value of an elementary charge is independent of velocity.

Properties of Charge

• Charge produces electric fields and magnetic fields.
• A charged particle at rest produces only an electric field, while a moving charge produces both electric and magnetic fields.
• An accelerated charge radiates energy in the form of electromagnetic waves.
• Charge is quantized, meaning it can only take on discrete values.
• The smallest unit of charge is the charge of an electron, which is -1.6 × 10^(-19) C.

Comparison of Charge and Mass

• Electric charge can be positive, negative, or zero, while mass is always positive.
• The charge carried by a body does not depend on its velocity, while mass increases with velocity.
• Charge is quantized, while the quantization of mass is yet to be established.
• Electric charge is conserved, while mass is not conserved and can be converted into energy.
• The force between charges can be attractive or repulsive, while the gravitational force between two masses is always attractive.

Methods of Charging

• A body can be charged by friction, which involves the transfer of electrons from one body to another.
• Friction can cause one body to become positively charged and the other negatively charged.
• Charging by friction involves the conservation of charge, resulting in equal amounts of positive and negative charges.
• Other methods of charging include electrostatic induction.