Question

1) My 14V car battery could be used to charge my laptop, but I need to use an inverter to first convert it to a standard 120V. Then my laptop charge cord has a resistor inside which ensures that 1.6A of current flow through to the laptop. What is the resistance in the charge cord?
2) My laptop charge cord actually has another inverter inside tat converts the electricity to 19.5V and 3.33A. What is the resistance in the cord that accomplishes this?

Answer 1

Answer:

1) Charge chord resistance is 75 Ω

2) Charge chord resistance is 6.33 Ω

Explanation:

1) To answer the question, we note that the the formula voltage is found as follows;

V = IR

Therefore,

$R = \frac{V}{I} = \frac{120}{1.6} = 75 \, \Omega$

2) Where the voltage, V = 19.5 V and the current, I = 3.33 A, we have;

Initial resistance R₁ = 19.5 V/(3.33 A) = 5.86 Ω

However, to reduce the current to 1.6 A, we have;

$R_T = \frac{19.5}{1.6} = 12.1875 \ \Omega$

Therefore, where the resistance is found by the sum of the total resistance we have;

$R_T$ = R₁ + Charge chord resistance

∴ 12.1875 = 5.86 + Charge chord resistance

Hence, charge chord resistance = 6.33 Ω