You have discovered that voltage and resistance both have an effect on the current flowing in a circuit. Other factors being constant, an increase in voltage results in an increase in current. On the other hand, an increase in resistance results in a decrease in current.
In 1826 Georg Ohm discovered this relationship and developed a mathematical law of electric current. This is now known as Ohm's Law.
Therefore, if the resistance is kept constant, then doubling the voltage doubles the current. Conversely, if the voltage is constant then doubling the resistance halves the current. There is a very simple relationship between all three variables as you can see.
Using the symbols V for voltage, R for resistance and I for current the formula for Ohm's Law is: V = R × I.
Note: Ohm's Law is stated for a conductor at a constant temperature. Usually as temperature rises in a wire or resistor, resistance also rises.
Putting these into words Ohm's Law states that:
A triangle to make it easy to remember
Ohm's Law at work
The current is needed so the required formula is:
current = voltage divided by resistance or I = V/R.