Final answer:
To determine the current in the 400-Ω resistor when r = 200-Ω, we can use Ohm's law. We find the voltage across the resistor R₁ using the current and resistance values for the other resistors, and then calculate the current through R₁ using Ohm's law.
Step-by-step explanation:
To determine the current in the 400-Ω resistor (let's call it R₁) when r = 200-Ω, we can use Ohm's law. Ohm's law states that the current flowing through a resistor is equal to the voltage across the resistor divided by the resistance. In this case, we need to find the voltage across the resistor R₁ when r = 200-Ω.
To find the voltage across R₁, we can use the formula:
V = i × R, where V is the voltage, i is the current, and R is the resistance.
Since we know the current through resistors R₁, R₂, R₃, and R₄ when r = 200-Ω is 0.48 A, 0.30 A, 1.2 A, and 0.24 A, respectively, we can use the relevant value of i. The voltage across R₁ is:
V = i × R = 0.48 A × 400-Ω = 192 V
Therefore, the current in the 400-Ω resistor (R₁) when r = 200-Ω is 192 V/400-Ω = 0.48 A.