Electrical Power and Resistance Concepts

Wattage

• Energy is quantified in joules (J), while power, a measure of energy over time, is quantified as joules per second.
• The SI unit for power is the watt, abbreviated as W, represented as 1 W = 1 joule/second (J/s).

Calculating Power

• Electric power denotes the rate at which energy is transferred and is also expressed in watts (W) or joules per second (J/s).
• Voltage (V) indicates potential energy expressed in joules per coulomb (J/C), while current (I) measures the flow of charge in amperes (A), or coulombs per second (C/s).
• Power can be calculated using the relationship: Power (W) = Voltage (V) × Current (A).

Power Ratings

• Electronic components convert energy from one form to another, resulting in both desired transfers (e.g., LEDs lighting, motors spinning) and undesirable power losses, typically manifested as heat.
• Excessive power loss can lead to overheating and potential damage to components.

Resistor Power Ratings

• Resistors often contribute to power loss, where voltage across them induces current flow.
• Increased voltage results in increased current and power dissipation.
• Example: A 10Ω resistor dissipates 8.1W with a 9V drop, exceeding typical ratings; most resistors operate between ⅛W (0.125W) and ½W (0.5W).
• Applying too much power, like 8W on a standard ½W resistor, poses significant risk for overheating.

Producers and Consumers

• Components in a circuit are classified as either consumers or producers of electrical energy.
• Consumers, such as LEDs, transform electrical energy into other forms (e.g., light).
• Producers, like batteries, convert energy from other forms into electrical energy for the circuit.