Tag: electro-magnetism

 A transformer is a device that is used to either raise or lower voltages and currents in an electrical circuit. In modern electrical distribution systems, transformers are used to boost voltage levels so as to decrease line losses during transmission

Answer is D.

Soft iron are ferromagnetic materials made of iron which can be magnetized and demagnetized easily. This is an advantage in transformers because in transformers, we're constantly varying magnetism of the core. This is important because without the change of magnetism of the core, there wouldn't be any voltage induced in the second circuit (the output)! Hence, using a soft iron would allow the magnetism of the core to be changed easily, lessening the amount of energy lost and increasing the efficiency of the transformer. 
Hence, soft iron is used to make core of the transformer.

To obtain suitable AC voltage so that energy loss is avoided.

Soft iron provides the best material for the core of a transformer as its permeability $(\mu)$ is very high. Its hysteresis curve is of small area and its coercivity is very low.

Transformer works only for alternating current because there will be no flux linked with the coil of transformer as the voltage is constant.

A transformer consists of a primary coil and the secondary coil. The current from the primary coil is induced into the secondary coil. Since there is the involvement of two coils mutually, it is termed as mutual induction.

C

Transformer is a static device which transforms electrical energy from one circuit to another and with the help of mutual inductor between two windings. The transformer may be step up or step down. A transformer that increases voltage from primary to secondary (more secondary windings turns than primary winding turns) is called step up transformer. Conversely a transformer designed to do just the opposite is called step down transformer. 

A transformer is based on the principle of mutual inductance , and it is used to change the alternating voltage . The transformer which increases the voltage is called step-up transformer , and which decreases is step-down transformer .

The transformer works on the principle of mutual induction. The voltage in one coil changes to change the magnetic field that it creates. This changing magnetic field causes a flux change in the secondary coil, which would create an induced emf in the coil. Thus it is necessary to have a changing magnetic field in a transformer to cause induction in secondary coil.

Working of transformer is based on the conservation of power i.e no power is lost inside the transformer.