188Fundamental Electrical and Electronic Principles 5.24 Transformer Voltage and Current Ratios Let us consider an ideal transformer. This means that the resistance of the windings is negligible, and there are no core losses due to hysteresis and eddy currents. Also, let the secondary be connected to a purely resistive load, as shown in Fig. 5.43 . N1 : N2V2V1 Fig. 5.42 N1:N2V2I2I1RLV1E1E2 Fig. 5.43 Under these conditions, the primary back emf, El , will be of the same magnitude as the primary applied voltage, V1 . The secondary terminal voltage, V2 , will be of the same magnitude as the secondary induced emf, E2 . Finally, the output power will be the same as the input power. The two emfs are given by ENtENt1122ddvolt, and ddvolt so,the primary. If the secondary is connected to a load, then it will cause the secondary current I2 to ﬂ ow. This results in a secondary terminal voltage, V2 . Figure 5.42 shows the circuit symbol for a transformer.