Fundamental Electrical and Electronic Principles, Third Edition

188 Fundamental Electrical and Electronic Principlesthe primary. If the secondary is connected to a load, then it will cause thesecondary current I 2 to flow. This results in a secondary terminal voltage,V 2 . Figure 5.42 shows the circuit symbol for a transformer.N 1 : N 2V 2V 1Fig. 5.425.24 Transformer Voltage and Current RatiosLet us consider an ideal transformer. This means that the resistanceof the windings is negligible, and there are no core losses due tohysteresis and eddy currents. Also, let the secondary be connected to apurely resistive load, as shown in Fig. 5.43 .I 1N 1 :N 2 I 2V 2V1 E 1 E 2R LFig. 5.43Under these conditions, the primary back emf, E l , will be of the samemagnitude as the primary applied voltage, V 1 . The secondary terminalvoltage, V 2 , will be of the same magnitude as the secondary inducedemf, E 2 . Finally, the output power will be the same as the input power.The two emfs are given byE1N1 d Φvolt, and Edt2N2 dΦvolt so,dt