A laptop charger needs to convert 230 V from a wall outlet to 9.0 V to charge the laptop battery safely. If the charger is rated at 20 W (i) determine the current in the primary coil of the charger's transformer (ii) calculate the resistance of the charging element.

• A. (i) I_p = 2.5 × 10^-2 A (ii) R = 3.3 Ω
• B. (i) I_p = 2.5 × 10^-2 A (ii) R = 4.1 Ω
• C. (i) I_p = 8.7 × 10^-2 A (ii) R = 3.3 Ω
• D. (i) I_p = 8.7 × 10^-2 A (ii) R = 4.1 Ω