Final answer:
In a simple circuit, replacing a 10 Ω resistor with a 20 Ω resistor doubles the resistance, which according to Ohm's law results in halving the current if the voltage remains constant.
Step-by-step explanation:
If a 10 Ω resistor is removed from a simple circuit and replaced by a 20 Ω resistor, the resistance in the circuit increases. According to Ohm's law (I = V/R), if the voltage (V) across the circuit remains constant, increasing the resistance (R) will result in a decrease in the current (I). Specifically, replacing a 10 Ω resistor with a 20 Ω resistor will double the resistance, which means the current will decrease to half its original value, assuming all other conditions in the circuit remain the same.
Ohm's law provides the foundational principle for analyzing simple circuits, indicating the direct relationship between voltage, current, and resistance. In practice, if the current was initially 1 A with the 10 Ω resistor, with a 20 Ω resistor replacing it, the current would become 0.5 A.