Let’s Do It Creatively ... and Environmentally with Renewable Energy (CERE)”.

b)

Energy needs to be converted because power stations transmit energy as High Voltage Direct Current or just Direct Current, a form of current and voltage which is unsuitable for domestic use.  Tesla showed it was cheaper and easier to use AC but Edison argued that DC was safer because the technological change would cause his business to go bankrupt. Also energy needs to be changed from ac to dc due to domestic appliances like mobile phones and laptop computers. Energy is converted through use of transformers; a transformer is an electrical

device that transfers electrical energy from one circuit to another.   

Basically, a transformer changes electricity from high to low voltage using two properties of electricity. In an electric circuit, there is magnetism around it. Second, whenever a magnetic field changes (by moving or by changing strength) a voltage is made.

If there's another wire close to an electric current that is changing strength, the current of electricity will also flow into that other wire as the magnetism changes.

A transformer takes in electricity at a higher voltage and lets it run through lots of coils wound around an iron core. Because the current is alternating, the magnetism in the core is also alternating. Also around the core is an output wire with fewer coils. The magnetism changing back and forth makes a current in the wire. Having fewer coils means less voltage. So the voltage is "stepped-down."

Energy is lost during the conversion of electrical energy. Losses in the transformer arise from:

Winding resistance - Current flowing through the windings causes resistive heating of the conductors. At higher frequencies, skin effect and proximity effect create additional winding resistance and losses.

Hysteresis losses- Each time the magnetic field is reversed, a small amount of energy is lost due to hysteresis within the core. For a given core material, the loss is proportional to the frequency, and is a function of the peak flux density to which it is subjected.

Eddy currents -Ferromagnetic materials are also good conductors, and a solid core made from such a material also constitutes a single short-circuited turn throughout its entire length. Eddy currents therefore circulate within the core in a plane normal to the flux, and are responsible for resistive heating of the core material. The eddy current loss is a complex function of the square of supply frequency and Inverse Square of the material thickness.

Magnetostriction-Magnetic flux in a ferromagnetic material, such as the core, causes it to physically expand and contract slightly with each cycle of the magnetic field, an effect known as magnetostriction. This produces the buzzing sound commonly associated with transformers, and in turn causes losses due to frictional heating in susceptible cores.

Mechanical losses -In addition to magnetostriction, the alternating magnetic field causes fluctuating electromagnetic forces between the primary and secondary windings. These incite vibrations within nearby metalwork, adding to the buzzing noise, and consuming a small amount of power.

Stray losses-Leakage inductance is by itself lossless, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle. However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat.

(Taken from unknown and various sources for GCSE 

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