A battery drives current through a single resistor. Adjust the voltage and resistance values. The ammeter reading always equals the voltage divided by the resistance. This relationship is Ohm's law.
I = 5.0 V ÷ 1000 Ω = 5.0 mA
Hold the resistance constant and raise the voltage, and the current increases proportionally. Hold the voltage constant and raise the resistance, and the current decreases. Current always equals V divided by R, without exception.