If you had resistors with values of 10Ω and 20Ω. What would the current vs voltage graph look like? The 10 Ω resistor is first and then replace with the 20Ω
In both cases we get two straight lines.
The slope of the straight line for 20 ohms = 2*slope of the straight line for 10 ohms.

If you had resistors with values of 10Ω and 20Ω. What would the current vs voltage...