1. AC Electricity

2. What is Alternating Current??? 1.Alternating current (AC) electricity is the type of electricity commonly used in homes and businesses throughout the world. 2.While direct current (DC) electricity flows in one direction through a wire, AC electricity alternates its direction in a back-and-forth motion. 3.The direction alternates between 50 and 60 times per second, depending on the electrical system of the country. 4.AC electricity is created by an AC electric generator, which determines the frequency. 5.What is special about AC electricity is that the voltage can be readily changed, thus making it more suitable for long-distance transmission than DC electricity.

5. Difference between AC and DC electricity Electrons move direct with DC electricity With DC electricity, connecting a wire from the negative ( − ) terminal of a battery to the positive (+) terminal will cause the negative charged electrons to rush through the wire toward the positive charged side. Electrons alternate directions in AC electricity With an AC generator, a slightly different configuration alternates the push and pull of each generator terminal. Thus the electricity in the wire moves in one direction for a short while and then reverses its direction when the generator armature is in a different position.

6. Transforming voltages AC voltages can be readily transformed to higher or lower voltage levels, while it is difficult to do that with DC voltages. High voltages are more efficient for sending electricity great distances This is because the high voltages from the power station can be easily reduced to a safer voltage for use in the house. Tuning circuits AC electricity also allows for the use of a capacitor and inductor within an electrical or electronic circuit. These devices can affect the way the alternating current passes through a circuit. They are only effective with AC electricity. Advantages of AC electricity

9. Properties of Alternating Current Frequency. commonly measured in cycles per second (cycles/sec) units of Hertz It ranges from 5 to 60 Hz Period. amount of time required to complete one cycle of the waveform measured in seconds/cycle AC power at 50 Hz will have a period of 1/50 = 0.02 seconds/cycle Wavelength. Wavelength is very similar to period as discussed above, except that wavelength is measured in distance per cycle where period is measured in time per cycle. Amplitude. how positive or negative the voltage is

10. Evenly Alternating Currents Sinusoidal Currents Evenly alternating sine wave currents 50 Hz Gives 100 pulses It is produced from the mains by reducing the voltage to 60-80 V with a step down transformer Usually surged to cause rhythmical muscle contractions It relieves pain & oedema

11. AC Generator

12. A/C generator / Dynamo Machine which produces alternating current from mechanical energy It is based on the phenomenon of electromagnetic induction Whenever amount of magnetic flux linked with the coil changes an EMF is induced in the coil The direction of current is given by Fleming’s right hand rule.

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