Final answer:
Load is matched to a transmission line when the load impedance is equal to the characteristic impedance of the line, resulting in maximum power transfer and minimizing power losses.
Step-by-step explanation:
In transmission lines, a load is matched when the impedance of the load is equal to the characteristic impedance of the transmission line. This is important because when the load is matched to the transmission line, maximum power transfer occurs, minimizing power losses. The matching of the load to the transmission line can be achieved by using impedance matching techniques such as using matching transformers or adjusting the load impedance.
For example, in a power transmission system, if the load impedance is lower than the characteristic impedance of the transmission line, there will be reflection of power back to the source, causing power loss. On the other hand, if the load impedance is higher than the characteristic impedance, there will be a mismatch resulting in inefficient power transfer.