Let's solve each part step by step: --- ## (i) **Unit of Current and Types of Current** ### **Unit of Current** - The unit of electric current is the **ampere (A)**. ### **Two Common Types of Current** 1. **Direct Current (DC):** - **Definition:** Electric current flows in one direction only. - **Source Example:** Batteries. - **Figure:** ``` DC: ──────────→ ``` 2. **Alternating Current (AC):** - **Definition:** Electric current changes direction periodically. - **Source Example:** Mains electricity (household supply). - **Figure:** ``` AC: ~~~~~~~ (sinusoidal wave) ``` --- ## (ii) **Stove Element Power Consumption** Given: - Current, \( I = 15\, \text{A} \) - Voltage, \( V = 240\, \text{V} \) - Energy to be consumed, \( E = 60\, \text{kJ} = 60,000\, \text{J} \) ### **Step 1: Calculate Power** \[ P = V \times I = 240\, \text{V} \times 15\, \text{A} = 360\, \text{W} \] ### **Step 2: Calculate Time to Consume 60 kJ** \[ E = P \times t \implies t = \frac{E}{P} \] \[ t = \frac{60,000\, \text{J}}{360\, \text{W}} = 16.67\, \text{seconds} \] **Answer:** It takes **16.67 seconds** to consume 60 kJ. --- ## (iii) **Annual Cost of Running PC and Bulb** **Given:** - PC: \( 120\, \text{W} \) for 4 h/day - Bulb: \( 60\, \text{W} \) for 8 h/day - Energy cost: $.12/kWh ### **Step 1: Daily Energy Used** - PC: \( 120\, \text{W} \times 4\, \text{h} = 480\, \text{Wh} = .48\, \text{kWh} \) - Bulb: \( 60\, \text{W} \times 8\, \text{h} = 480\, \text{Wh} = .48\, \text{kWh} \) - Total per day: \( .48 + .48 = .96\, \text{kWh} \) ### **Step 2: Annual Energy Used** \[ \text{Annual Energy} = .96\, \text{kWh/day} \times 365\, \text{days} = 350.4\, \text{kWh} \] ### **Step 3: Annual Cost** \[ \text{Annual Cost} = 350.4\, \text{kWh} \times \$.12/\text{kWh} = \$42.05 \] **Answer:** The household pays **\$42.05 per year** to run the PC and the bulb. --- ### **Summary Table** | Appliance | Power (W) | Hours/Day | kWh/Day | kWh/Year | Cost/Year ($) | |-----------|-----------|-----------|---------|----------|--------------| | PC | 120 | 4 | .48 | 175.2 | 21.02 | | Bulb | 60 | 8 | .48 | 175.2 | 21.02 | | **Total** | | | .96 | 350.4 | 42.05 | --- ## **Let me know if you want diagrams or further explanation!**