SS3 Second Term Physics Lesson Note – Transformer and Power Transmission

The content is just an excerpt from the complete note for SS3 Second Term Physics Lesson Note – Transformer and Power Transmission. Check below to download the complete DOCUMENT

TRANSFORMER AND POWER TRANSMISSION

A transformer is an electrical device for changing the size of an a.c. voltage. It acts to increase or decrease the em.f of an alternating current.  It consists of two separate sets of coil, the primary coil and the secondary coil.  The primary coil is the input winding of turns of wire and the secondary coil is the output winding.  The coils are wound round a soft-iron core. The soft-iron core acts to increase and concentrate the magnetic flux within the core. It is also laminated, i.e. it consists of sheets of soft-iron insulated from each other instead of a solid block of iron.  This lamination reduces loss of energy in the form of heat due to eddy currents introduced in the core.

STEP DOWN TRANSFORMER

When an alternating e.m.f. or a.c voltage (EP) is applied at the terminals of the primary coil (p), an alternating magnetic flux is produced in the iron core which links or threads the secondary coil (s). An alternating e,m,f (Es) of the same frequency as that Ep is induced in the secondary coil by mutual inductance.

Mutual inductance is the flow of induced current or voltage in a coil due to an alternating or varying current in a neighbouring coil.

The total flux linking the two coils is proportional to their number of turns. The induced e.m.f in the secondary coil (Ep) depends on the e.m.f. in the primary coil and on the ratio of the number of turns in each

:.    ES      =    Ns

EpNp

In an ideal transformer with a 100% efficiency, the power developed in the secondary coil is equal to the power developed in the primary coil.

:.   Es=  Ip

Ep       Is

Hence,  Es = Ns     = Ip

EpNp       Is.

To use a transformer to increase an applied  voltage, i.e to make Es greater than Ep, Ns must be grater than Np . such a transformer which increases or steps up the applied or primary voltage is called a step-up transformer. In a step-up, the primary current is greater than the secondary current but the primary voltage is less than the secondary voltage.

To gain full access to the note: DOWNLOAD FILE