The ammeter reads 0.5 amps.
A 2 ohm resistor* is twice as resistant as a 1 ohm resistor,
so it is twice as hard for the current* to flow.
The resistor allows half of the 1 amp current to pass.
By Ohm's Law:
V = IR
Solving for I:
Now replacing the symbols with the values given:
0.5 = I
I = 0.5 amps