question: Why can you plug an (AC) electical plug backwards in to a socket and it still works?
comment: AC stands for alternating current. The flow goes one way, then the other way, really fast. The device is receiving alternating no matter which way you plug it in.
passages: The points allow the coil magnetic field to build. When the points open by a cam arrangement, the magnetic field collapses inducing an EMF in the primary that is much larger than the battery voltage and the transformer action produces a large output voltage (20 kV or greater) from the secondary.
   External power supplies are used both with equipment with no other source of power and with battery-powered equipment, where the supply, when plugged in, can sometimes charge the battery in addition to powering the equipment.
   Adapters with AC outputs may consist only of a passive transformer (plus a few diodes in DC-output adapters), or they may employ switch-mode circuitry. AC adapters consume power (and produce electric and magnetic fields) even when not connected to a load; for this reason they are sometimes known as "electricity vampires", and may be plugged into power strips to allow them to be conveniently turned on and off.
  
  Section::::Types.:Programmable power supply.
   In each case, the upper right output remains positive, and lower right output negative. Since this is true whether the input is AC or DC, this circuit not only produces a DC output from an AC input, it can also provide what is sometimes called "reverse-polarity protection". That is, it permits normal functioning of DC-powered equipment when batteries have been installed backwards, or when the leads (wires) from a DC power source have been reversed, and protects the equipment from potential damage caused by reverse polarity.
   In Italy, the system was never definitively abandoned. Though very rarely seen today, it is still marked as available in BTicino’s catalogue, (except for the three-phase version, which stopped production in July 2011).
   If the output is required to be isolated from the input, as is usually the case in mains power supplies, the inverted AC is used to drive the primary winding of a high-frequency transformer. This converts the voltage up or down to the required output level on its secondary winding. The output transformer in the block diagram serves this purpose.
   SI 32 plugs have no sleeve insulation, so when a plug is partially removed its prongs may still be powered although they can be touched by small fingers, metal objects, etc., with a risk of electric shock.
  
  Sockets have a defined polarity; looking at the front, neutral is to the left, earth at the bottom, and line to the right.
  
  Section::::Types in present use.:Italy (Type L).
   As a DC power connector, it has the disadvantages of bulkiness, relatively low current rating, and poor contact reliability. However, due to it's large diameter, the connector and appliances can have a robust design against damage such as bending. Additionally, the connector is reversible.
   BULLET::::- Distributors allowed an output pulse to be wired to more than one input without creating a back circuit between the inputs.
   Adjusting the frequency and phase requires an AC to DC to AC converter. This is usually constructed from very large IGBT semiconductors. The converter is bidirectional, and can pass power in either direction. Power can flow from this winding as well as from the output winding.
  
  Section::::History.
   The male plug is sometimes used to feed power "into" a vehicle to recharge its battery, because it usually has no regulatory circuitry between the outlet and the car battery. For instance, portable solar battery maintainers generally connect to a vehicle's battery in this manner. Trickle chargers also sometimes connect in this way, eliminating the need to leave a vehicle's hood open, as well as eliminating the possibility of reversed polarity. Most cars nowadays are designed with a battery-negative earthing system and therefore have +12v positive power distribution. In such case the centre pin of a plug/socket will be +12V DC and the outer casing 0V. While polarity is not an issue for a cigarette lighter, it is prudent to verify correct matching of polarities when connecting other kinds of accessory. In some models, the cigarette lighter outlet is not powered when the ignition key is removed and charging is not possible.
   In practice this case usually does not happen because the pickup cartridge, an inductive voltage source, need have no connection to the turntable metalwork, and so the signal ground is isolated from the chassis or protective ground at that end of the link. Therefore, there is no current loop, and no hum problem due directly to the grounding arrangements.
   A simple example is a large bank of capacitors that are added to a branch, left charged up and normally disconnected by a switch. In the event of a failure, the capacitors are switched into the branch by the utility after a short delay. This can be easily accomplished through automatic means at the point of distribution. The capacitors can only supply current for a brief period, ensuring that the start or end of the pulse they deliver will cause enough of a change to trip the inverters.
   Opposite potentials are induced in the secondary when the interrupter 'breaks' the circuit and 'closes' the circuit. However, the current change in the primary is much more abrupt when the interrupter 'breaks'. When the contacts close, the current builds up slowly in the primary because the supply voltage has a limited ability to force current through the coil's inductance. In contrast, when the interrupter contacts open, the current falls to zero suddenly. So the pulse of voltage induced in the secondary at 'break' is much larger than the pulse induced at 'close', it is the 'break' that generates the coil's high voltage output.
   A common EPS must include a cable with a micro USB-B connector for connecting to a mobile phone. This cable can be either "captive" (permanently attached to the power supply) or detachable. If detachable, the cable must connect to the power supply via a standard USB type-A plug.
   Few private houses in Brazil have an earthed supply, so even if a three-pin socket is present it is not safe to assume that all three terminals are actually connected. Most large domestic appliances were sold with the option to fit a flying earth tail to be locally earthed, but many consumers were unsure how to use this and so didn't connect it. The new standard has an earth pin, which in theory eliminates the need for the flying earth tail.
  
  Section::::Types in present use.:British and compatible standards.
   Relying on the neutral conductor was a legal grounding method for electric ranges and clothes dryers, under the National Electrical Code from the 1947 to the 1996 editions. Since North American dryers and ranges have certain components (timers, lights, fans, etc.) that run on 120 V, this means that the neutral wire indirectly used for grounding would also carry current, even under non-fault conditions. Although this is contrary to modern grounding practice, such "grandfathered" installations remain common in older homes in the United States.
  
  Section::::Non-locking connectors.:NEMA 11.
   If the engine was rotated while examining the wave-form output of the coil with an oscilloscope, it would appear to be AC. Since the charge-time of the coil corresponds to much less than a full revolution of the crank, the coil really 'sees' only DC current for charging the external ignition coil.
   If the upper portion of the plates is foreshortened, as in Fig. 3, a traveling-wave field of finite amplitude then exists at the upper open end, and if the dominant NRD guide mode is fast (it can be fast or slow depending on the frequency), power will be radiated away at an angle from this open end.
   Devices that require alternating-current mains electricity can be operated with a plug-in inverter, which outputs voltage levels and patterns similar to the home electrical outlet.
   When an electric current is passed through the coil it generates a magnetic field that activates the armature, and the consequent movement of the movable contact(s) either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing.
   A standard socket-outlet in Australia provides a nominal voltage of 230 volts RMS at a maximum of 10 amps and always includes an earth connection. "Shuttered" socket-outlets are available, but these are not required by regulation.
   An AFCI does not detect high line voltage due to an open neutral in a multiwire branch circuit. A multiwire branch circuit has both energized wires of a 120-240 V split phase service. If the neutral is broken, devices connected from a 120 V leg to the neutral may experience excess voltage, up to twice normal.
   Since the cigarette lighter socket was originally designed only to heat a cigarette lighter, repurposing these sockets as generic power connectors can lead to many problems. In addition to the issues with partially-compatible physical dimensions, the plugs can vibrate out of the socket under normal driving conditions, owing to poor retention. Also, there have been reports of melted plug tips due to poor contact and heat generation from ohmic resistance. Non-vehicular use in stationary settings may avoid vibration problems when used as an alternative to 120 volt AC outlets, but low-quality connectors may still develop high resistance or intermittent contact.
   In Brazil, similar plugs and sockets are still commonly used for high-power appliances like air conditioners, dishwashers, and household ovens. Although being often called "Argentinian plug," it is actually based on the American NEMA 10-20 standard, and is incompatible with Argentinian IRAM plugs. Since Brazil adopted the NBR 14136 standard which includes a 20 A version, the original motivation to use the NEMA 10-20 plug has ceased to exist.
  
  Section::::Types in present use.:Australian/New Zealand standard AS/NZS 3112 (Type I), used in Australasia.
  
presuppositions: Plugging an (AC) electical plug backwards into a socket should not work.
corrections: Alternating Current (AC) flows alternating directions quickly, no matter which way it is plugged in.
raw_presuppositions: Plugging an (AC) electical plug backwards into a socket should not work. Plugging an (AC) electical plug backwards into a socket and should not work.
raw_corrections: Alternating Current (AC) flows alternating directions quickly, no matter which way it is plugged in. Alternating Current (AC) flows alternating directions quickly, no matter which way it is plugged in.