Examples of Power Dissipation in Electric Heaters and Light Bulbs

📚 Quick Study Guide

• ⚡ Power Dissipation: The rate at which electrical energy is converted into other forms of energy, like heat or light.
• 💡 Electric Heaters: Primarily convert electrical energy into heat due to the resistance of the heating element.
• 🔦 Light Bulbs: Convert electrical energy into both heat and light. Incandescent bulbs produce more heat than light.
• 🔢 Power Formula: The power dissipated in a resistor (like the heating element or light bulb filament) is given by $P = I^2R = \frac{V^2}{R} = IV$, where $P$ is power, $I$ is current, $R$ is resistance, and $V$ is voltage.
• 🌡️ Joule's Law: Describes the heat produced by a current flowing through a conductor: $Q = I^2Rt$, where $Q$ is the heat generated, $I$ is the current, $R$ is the resistance, and $t$ is the time.
• ✨ Efficiency: The ratio of useful energy output (light in a light bulb) to the total energy input. Light bulbs are generally not very efficient, as a large portion of the energy is converted to heat.

🧪 Practice Quiz

1. Which of the following best describes power dissipation in an electric heater?
   1. Converting heat energy into electrical energy.
   2. Converting electrical energy into kinetic energy.
   3. Converting electrical energy into heat energy.
   4. Converting chemical energy into electrical energy.
2. A light bulb primarily dissipates power in the form of:
   1. Sound and light.
   2. Heat and sound.
   3. Light only.
   4. Heat and light.
3. What formula correctly calculates the power dissipated by a resistor, given current (I) and resistance (R)?
   1. $P = V/I$
   2. $P = I^2R$
   3. $P = V^2/I$
   4. $P = IR$
4. According to Joule's Law, what happens to the heat generated if the current through a resistor doubles?
   1. It doubles.
   2. It quadruples.
   3. It halves.
   4. It remains the same.
5. Which type of light bulb is generally less efficient due to higher heat production?
   1. LED
   2. CFL
   3. Incandescent
   4. Halogen
6. If a 100W light bulb is connected to a 120V power source, what is the current flowing through it (approximately)?
   1. 0.53 A
   2. 1.2 A
   3. 0.83 A
   4. 1.5 A
7. The efficiency of a light bulb is defined as:
   1. Total energy input divided by useful light output.
   2. Useful light output divided by total energy input.
   3. Total heat output divided by total energy input.
   4. Total energy input divided by total heat output.