In a transformer, which coil is connected to the supply?

In a transformer, the primary coil is the one that is connected to the supply voltage. This coil receives electrical energy from the power source and creates a magnetic field around it. The operation of the transformer is based on this magnetic field, which induces a voltage in the secondary coil through the process of electromagnetic induction.

When an alternating current flows through the primary coil, it generates a changing magnetic field inside the transformer core. This changing magnetic field then induces an alternating voltage in the secondary coil, which is designed to output a different voltage, either higher or lower than the supply voltage, depending on the turns ratio between the primary and secondary coils.

The secondary coil, in contrast, is where the induced current flows to power devices or systems connected to it, but it is not connected directly to the supply. The other options, such as core coil and inductive coil, do not represent specific roles in the context of connecting to a supply. The core is simply the magnetic structure that enhances the efficiency of the transformer, while inductive coil could refer to various types of inductors, not specifically within the transformer context.