Voltage, Current & Resistance
- Define voltage and understand its role in electrical circuits
- Explain current and the different types of current
- Understand resistance and what affects it
- Apply the relationships between voltage, current, and resistance
Voltage (Electric Potential Difference)
Voltage, also called electric potential difference, is the force that pushes electric charges through a conductor. Think of it like pressure in a water pipe—it provides the "push" that moves electrons.
Where: V = Voltage in Volts (V), W = Work/Energy in Joules (J), Q = Charge in Coulombs (C)
Voltage Sources
| Source | Voltage | Application |
|---|---|---|
| AA Battery | 1.5V | Small electronics |
| Car Battery | 12V | Automotive systems |
| Wall Outlet (US) | 120V | Household power |
| Wall Outlet (EU) | 230V | Household power |
| Transmission Line | up to 765kV | Power distribution |
Current (Electric Flow)
Current is the flow of electric charge through a conductor. It's measured in Amperes (A), where 1 Ampere = 1 Coulomb per second.
Types of Current
- Direct Current (DC): Current flows in one direction only (batteries, solar panels)
- Alternating Current (AC): Current reverses direction periodically (household power)
Resistance
Resistance is the opposition to current flow. It's measured in Ohms (Ω), named after Georg Simon Ohm.
Where: ρ = Resistivity (Ω·m), L = Length (m), A = Cross-sectional area (m²)
Factors Affecting Resistance
- Length: Longer wire = more resistance
- Cross-sectional Area: Thicker wire = less resistance
- Temperature: Higher temperature = more resistance (in metals)
- Material: Copper has low resistance; nichrome has high resistance
Summary
- Voltage pushes current through a circuit (measured in Volts)
- Current is the flow of charge (measured in Amperes)
- Resistance opposes current flow (measured in Ohms)
- These three quantities are fundamental to all electrical calculations