Power in Electric Circuits: Definition and Real-World Examples

📚 Quick Study Guide

• ⚡ Power is the rate at which electrical energy is transferred in an electric circuit.
• 🔢 The standard unit of power is the watt (W).
• 💡 Power can be calculated using the following formulas:
  • $P = VI$ (Power = Voltage × Current)
  • $P = I^2R$ (Power = Current² × Resistance)
  • $P = \frac{V^2}{R}$ (Power = Voltage² / Resistance)
• 🏠 Real-world examples include light bulbs, heaters, and any electrical appliance.
• 🔥 Higher power rating means more energy consumption per unit of time.

🧪 Practice Quiz

1. Question 1: What is the standard unit of power?
   1. (A) Ampere
   2. (B) Volt
   3. (C) Watt
   4. (D) Ohm
2. Question 2: A circuit has a voltage of 12V and a current of 2A. What is the power?
   1. (A) 6W
   2. (B) 14W
   3. (C) 24W
   4. (D) 48W
3. Question 3: If a resistor of 10 ohms has a current of 3A flowing through it, what is the power dissipated?
   1. (A) 30W
   2. (B) 90W
   3. (C) 120W
   4. (D) 300W
4. Question 4: A 100W light bulb is connected to a 120V source. What is the current flowing through it?
   1. (A) 0.83A
   2. (B) 1.2A
   3. (C) 12A
   4. (D) 12000A
5. Question 5: Which of the following formulas is used to calculate power?
   1. (A) $P = IR$
   2. (B) $P = \frac{V}{I}$
   3. (C) $P = VI$
   4. (D) $P = \frac{R}{I}$
6. Question 6: What happens to the power dissipated in a resistor if the voltage across it is doubled?
   1. (A) It doubles
   2. (B) It quadruples
   3. (C) It halves
   4. (D) It remains the same
7. Question 7: A heater consumes 1500W of power when connected to a 120V supply. What is the resistance of the heater?
   1. (A) 0.08 ohms
   2. (B) 9.6 ohms
   3. (C) 14.4 ohms
   4. (D) 16 ohms