Fundamentals of Electricity: Charge, Current, and Voltage
Electricity: Powering Modern Life
Electricity is crucial for modern life, enabling lighting, television, music, and electrical appliances. Without it, our world would nearly grind to a halt.
What is Electricity?
Electricity is a natural interaction originating in the elementary particles forming atoms. The term derives from the Greek word elektron (amber).
Electric Charge
- Electric Charge: An intrinsic property of elementary particles, like mass. Electrons have a negative charge, and protons have a positive charge.
- Electrified Body: A body becomes electrified when it gains or loses electrons.
- Neutral Body: Bodies are typically neutral because their positive and negative charges are balanced.
Types of Electrification
- Electrification by Rubbing: Rubbing two materials together (e.g., wool and glass) transfers electrons, charging one positively and the other negatively.
- Electrification by Contact: Touching a neutral body with a charged one transfers electrons.
- Electrification by Induction: Bringing a charged body near a neutral one polarizes it, separating charges without contact.
Attraction and Repulsion
Like charges repel, and opposite charges attract (Benjamin Franklin).
Coulomb (C)
The unit of electric charge. 1 Coulomb equals the total charge of 6.25 x 1018 electrons.
Polarization
Rearrangement of electric charges within a body.
Static Electricity
Electric charge transfer without continuous circulation, seen as sparks on clothes.
Electric Current
The motion of electric charges through a conductor, enabling electrical appliances.
Current Intensity
The amount of charge passing through a conductor’s cross-section per unit time. Formula: I = Q / t (I = current, Q = charge, t = time).
Ampere (A)
The unit of electric current intensity (C/s). Submultiples include milliamperes (mA) and microamperes (µA).
Zero Current
No net flow of charge, though electrons move.
Types of Current
- Direct Current (DC): Electrons flow in one direction.
- Alternating Current (AC): Electron flow changes direction alternately.
Voltage
The capacity of an electric charge to move due to electric force; energy per unit charge. Standard household voltage is 220V (some countries use 110V).
Potential Difference
Similar to water flowing from a height, potential difference causes charges to move between points of different potential.
Volt (V)
The unit of voltage. 1 volt moves 1 coulomb of charge with 1 joule of energy.
Alessandro Volta
The volt is named after the Italian physicist who invented the battery in 1800.
Resistance
Opposition to the flow of electric charge, measured in ohms (Ω).
Factors Affecting Resistance
- Material resistivity
- Conductor length
- Conductor cross-section area
- Temperature
Resistivity
Each material’s inherent resistance to charge flow, depending on atomic structure and temperature.
Conductors vs. Insulators
Insulators have high atomic vibration, hindering electron flow. Conductors have minimal vibration, allowing easy electron movement.