When a fixed value resistor is applied with 10V voltage at both ends, the current is 0.5A. If the voltage at both ends of the resistor is 0, what is the resistance value?

When a fixed value resistor is applied with 10V voltage at both ends, the current is 0.5A. If the voltage at both ends of the resistor is 0, what is the resistance value?

Resistance is 20 ohm, regardless of whether there is voltage at both ends

When a voltage of 10V is applied at both ends of a resistor, the current passing through it is 100mA. If this resistor is connected with another resistor
When a voltage of 10V is applied at both ends of a resistor, the current passing through it is 100mA. If this resistor is connected in series with another resistor R, a voltage of 50V must be applied at both ends of them to make the current passing through them also 100mA. Then the resistance value of the resistor R in series with it is 100mA
A 200 Ω B 300 Ω C 400 Ω D500 Ω (please write the process and answer)

Original resistance R1 = U1 / I1 = 10V / 100mA = 10V / 0.1A = 100ohm
Let the series resistance be R2
U2=I2(R1+R2)
And I2 = I1 = 100mA = 0.1A
So 50 = 0.1 (100 + R2)
R2 = 400
Select c 400 Ω