2.1 Fundamentals of Electricity

Key Concepts

• Voltage
• Current
• Resistance
• Ohm's Law

Voltage

Voltage, often referred to as electric potential difference, is the force that pushes electric charges through a conductor. It is measured in volts (V) and is analogous to the pressure in a water pipe. Higher voltage means more force is applied to move the charges, similar to how higher water pressure pushes more water through a pipe.

For example, a common household outlet in the United States provides 120 volts, which is sufficient to power most household appliances.

Current

Current is the flow of electric charge through a conductor. It is measured in amperes (A) and represents the rate at which charges move. Think of current as the flow rate of water in a pipe, where more current means more charges are flowing per second.

In a simple circuit, if you connect a 12-volt battery to a small light bulb, the current flowing through the bulb will depend on the resistance of the bulb. More current will flow if the resistance is lower.

Resistance

Resistance is the opposition to the flow of electric current. It is measured in ohms (Ω) and can be thought of as the friction that slows down the flow of charges. Higher resistance means more opposition to the flow of current, similar to how a narrow pipe restricts the flow of water.

For instance, a high-resistance resistor in an electronic circuit will limit the amount of current that can flow through it, protecting sensitive components from damage.

Ohm's Law

Ohm's Law is a fundamental principle in electrical engineering that relates voltage, current, and resistance. It is expressed mathematically as:

\[ V = I \times R \]

where \( V \) is the voltage (in volts), \( I \) is the current (in amperes), and \( R \) is the resistance (in ohms). This law helps in understanding how changes in one parameter affect the others.

For example, if you know the voltage across a resistor and the resistance of the resistor, you can use Ohm's Law to calculate the current flowing through it. Conversely, if you know the current and resistance, you can calculate the voltage.