 Welcome to Reflected Load in a Transformer. The amount of current that flows through the primary coil of a transformer is affected by the load in the secondary. However, the resistance value of the load does not appear to the primary to be equal to its actual resistance. Instead, the actual resistance is determined by the load resistance value in the secondary along with the transformer's turns ratio. This effect, called Reflected Load, is what the source effectively sees. It determines how much primary current flows. This equation is used to calculate the amount of resistance that is reflected into the primary. It is the turns ratio squared times the load resistance. In a step-up transformer in which there are more turns in the secondary windings than in the primary, the reflected resistance is less than the actual load resistance. In the example below, the step-up transformer has a turns ratio of 1 to 5 and a load resistance of 100 ohms. The reflected resistance seen by the source is determined by the following calculations. A step-down transformer has fewer turns than the secondary windings than in the primary. The reflected resistance is therefore greater than the actual load resistance. This step-down transformer has a turns ratio of 5 to 1 and a load resistance of 100 ohms. The reflected resistance seen by the source is determined by the following calculations. Now, check your knowledge with the following four questions. You have completed this activity, Reflected Load in a Transformer.