We will use the Ohms Law to solve this problem
[tex]I=\frac{V}{R}[/tex]where V is the voltage, R is the resistance and I is the current
In our case we have
V=20V
R=50 Ω
We substitute the values
[tex]I=\frac{20}{50}=0.4A[/tex]The current that flows through the circuit is 0.4 A
