Answer:

The correct answer is option 'B': a varying magnetic field.

Explanation:

Transformer Basics:
A transformer is an electrical device that is used to transfer electrical energy between two or more circuits through electromagnetic induction. It consists of two coils, the primary coil and the secondary coil, which are wound around a common iron core. The primary coil is connected to the input voltage source, and the secondary coil is connected to the load.

Electromagnetic Induction:
Electromagnetic induction is the phenomenon by which a changing magnetic field in a conductor induces an electric current in a nearby conductor. According to Faraday's law of electromagnetic induction, the magnitude of the induced voltage in a coil is directly proportional to the rate of change of magnetic flux passing through the coil.

Voltage Induction in the Secondary Coil:
In a transformer, when an alternating current flows through the primary coil, it produces a varying magnetic field around it. This varying magnetic field then links with the turns of the secondary coil, inducing an electric current in the secondary coil. According to Faraday's law, this changing magnetic field induces a voltage across the secondary coil.

Role of Magnetic Field:
The voltage induction in the secondary coil of a transformer is mainly due to the varying magnetic field. The varying magnetic field produced by the alternating current in the primary coil is responsible for inducing an electric current in the secondary coil. The magnetic field lines created by the primary coil cut across the turns of the secondary coil, causing a change in the magnetic flux passing through the secondary coil. This change in magnetic flux induces a voltage across the secondary coil.

Importance of Iron Core:
The iron core in the transformer serves to enhance the magnetic coupling between the primary and secondary coils. It provides a low reluctance path for the magnetic field, minimizing the energy loss due to leakage flux. The iron core does not directly contribute to the voltage induction in the secondary coil but plays a crucial role in the efficient transfer of energy between the coils.

In conclusion, the voltage induced in the secondary coil of a transformer is mainly due to the varying magnetic field produced by the alternating current in the primary coil. The magnetic field lines cut across the turns of the secondary coil, leading to a change in magnetic flux and the subsequent induction of voltage. The iron core in the transformer enhances the magnetic coupling between the coils and minimizes energy loss.

Explanation:The transformer voltage induced in the secondary coil of a transformer is mainly due to:A varying magnetic field:- Transformers work on the principle of electromagnetic induction.- In a transformer, an alternating current (AC) is passed through the primary coil, which creates a varying magnetic field around it.- This varying magnetic field then induces an electromotive force (EMF) in the secondary coil.- The voltage induced in the secondary coil is directly proportional to the number of turns in the coil and the rate of change of the magnetic field.- Hence, the induced voltage in the secondary coil of a transformer is mainly due to the varying magnetic field created by the primary coil.