After using for some time, big transformers get heated up. This is due to the fact that 1. current produces heat in the transformers 2. hysteresis loss occurs in the transformers 3. liquid used for cooling gets heated Select the correct answer using the code given below.

Big transformers heat up due to internal energy losses that are converted into thermal energy. Statement 1 is correct because current flowing through the copper windings encounters resistance, leading to resistive loss (IR loss or copper loss), which generates heat [1]. Statement 2 is correct because hysteresis loss occurs in the magnetic core as the material is repeatedly magnetized and demagnetized by the alternating magnetic field, causing molecular friction that manifests as heat. Statement 3 is incorrect as a cause of heating; while the cooling liquid (oil) does get heated, this is a consequence of absorbing heat from the core and windings to dissipate it, rather than the primary source of the transformer's heat generation. Therefore, only the electrical and magnetic losses (1 and 2) are the fundamental causes of the heating.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.7.1 Practical Applications of Heating Effect of Electric Current > p. 190