Final answer:
A current repeater can be used to boost the loop current in a circuit, particularly important in long transmission lines to reduce power loss associated with resistance.
Step-by-step explanation:
A current repeater can be used when a loop cannot generate enough loop current. Current repeaters amplify the current in a circuit to ensure that it is sufficient for the circuit's requirements. This is often necessary when dealing with long transmission lines which may dissipate more power than they transmit if the current is not adequately maintained. Repeating or boosting the current helps in overcoming the resistance of the transmission line and reduces power loss due to the relation P=I²R, where P represents power, I represents current, and R represents resistance.