Distinguish between DC and AC current
Electricity is nothing but electrons moving along a conductor, like a wire that has been harnessed for energy. The difference between AC and DC has to do with the direction in which the electrons flow. In DC, electrons flow steadily in a single direction. In AC, electrons keep switching directions, sometimes going forwards and then going backwards. Scientists found that electrical and magnetic fields are related. DC power was generated from the works of Thomas Edison. Nikola Tesla preferred AC because it travels farther without losing energy and could transfer different amounts of power. AC generators gradually replaced Edison's DC battery system because AC is safer to transfer over the longer city distances and can provide more power. Another difference between AC and DC involves the amount of energy it can carry. Each battery is designed to produce only one voltage, and that voltage of DC cannot travel very far until it begins to lose energy.
In a power station, electricity can be made most easily and efficiently by using a motor to spin magnetic wire coils. The resultant voltage is always "alternating" by virtue of the motor's rotation. A voltage generally goes first positive then negative rather like turning a battery cell continually backwards and forwards. Now, alternating voltage can be carried around the county in cables far more efficiently than direct current where the voltage is fixed. So the electricity that arrives at your house is still alternating voltage. Electric light bulbs and fires can run quite happily fro 230 volts A.C. Other equipment such as televisions has an internal power supply which converts the 230 volts A.C. to a low D.C. voltage that is safe and acceptable to the electronic circuits.
AC is more commonly the way of current produced in the power plants as it's easier to produce. AC is usually used for transmission because DC cannot be run through a transformer, and the distribution is quite more efficient in AC. AC can provide more power easier and with higher efficiencies than DC. In the other day a battery can only produce DC. This is why portable electrical systems use DC.
In a direct current (DC) electrical circuit, the voltage (V in volts) is an expression of the available energy per unit charge which drives the electric current around a closed circuit. Increasing the resistance will proportionately decrease the current which may be driven through the circuit by the voltage.
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