A variable resistor is a resistor whose resistance can be adjusted by turning a knob. In a certain experiment a battery is connected to a variable resistor R. The potential difference across the resistor and the current through it are recorded for a number of settings of the resistor knob. Assume the battery can be modeled as an ideal potential source in series with an internal resistor.
The emf of the potential source is 6.2 volts and the internal resistance is 0.1 Ω. If the variable resistor is set for 0.5 Ω, what is the current through it?