alternating current flows in a sinusoidal pattern ,what does it mean?

Question

in domestic single phase system we have a phase line and a neutral line but we know know that a.c current is sinusoidal nature, my doubt is, in single phase line how would current reverses its direction, how would you justify the sine nature in a single line.

Answer 1

It goes in one direction for half a cycle and the other direction for the other half. The phase line goes between a positive and nenative voltage.

Answer 2

Power generators produce a sine wave and 3 phases. the transformers ( step up/ step down ) are wound Y. the neutral is a wire connected where the 3 points of the Y connect and goes to the ground and a neutral wire. The sub station in your town has step down transformers with 3 phases coming out of them. Commercial and industrial consumers get 3 phase power cause it's more efficient to operate induction motors and the motors are smaller/less expensive. To save wire/money you only get a ground, neutral wire and one of the 3 phases in your neighborhood. Other neighborhoods are hooked to the other phases. If one neighborhood is using more power than another the load will be balanced through the neutral/ground connection. The shape of the wave is due to the geometry of the magnets in the generator. This is easier to explain with paper and pencil. Maybe this answers some of your question.

More tidbits for the home owner. If you live in a old old house watch out. You could cook your goose very easily. The ground and neutral is connected together in the breaker box. There are two hot ( 110V ) buses in the breaker box. Two hot 110V wires goes to your cooking stove and the potential is 220V. A ground wire is connected to the metal frame for your protection.

The plug in receptacles for 110V stuff has a one hot 110V wire, neutral and a ground. In old houses the receptacles weren’t polarized. You could turn the plug either way and there wasn’t a ground wire. This was a dangerous configuration and killed many people. The wires were bare and ran through the house attached with ceramic insulators ( ouch, it hurts very much if you touch one of them). Later came polarized plugs and receptacles. The plug can only be turned one way to assure hot to hot and neutral to neutral connections. If you look you will see that one slit in the receptacles is shorter than the other. The short one is the hot. This keeps the neutral prong from being shoved into the hot connection and smoke testing you and the circuit breaker. It seems the neutral was connected to the metal case and the load. Later came a 3 prong receptacle that included a ground connection to be connected to the metal case of stuff. This is why. If you are holding a electric drill with a ungrounded metal case and the neutral wire came loose in the power cord for example. You will light up like a neon sign if your body has a good ground connection.

If your new electric drill has a plastic insulating case chances are it doesn’t have a polarized plug or a ground connection.

Watch out for the neutral wire cause it can be a hot wire also. Let me give you an example. Lets say you have a large life insurance policy and you tell your spouse not to turn on the TV while you’re working in the basement. Lets say you disconnect a neutral connection in a terminal case while standing in a puddle of water that your spouse accidentally spilled. If you are touching the neutral wire going to the TV your spouse will be spending the next 6 months in Hawaii.

Answer 3

I[t] = a sin(omega t)

where I[t] is the current at time t,
a is the current amplitude,
and omega is some constant related to the frequency.

What do you mean, "justify"?

Usually the source of the AC is a dynamo. It has a rotating magnetic field that crosses a stationary winding (or vice versa). The rotation produces more or less a sine curve.

A cool thing about a sine wave is when you differentiate it, you get another sine wave. This happens in a transformer. The output voltage is proportional to the _rate of change_ of the input current, because that current is setting up the magnetic field in the transformer, and it's the rate of change of that field that induces voltage in the secondary winding.

Answer 4

Well, say you simply reversed the wires on a battery 60 times a second. Then you'd generate a square wave AC voltage from a DC battery. And guess what? The first sinusoidal harmonic ("the fundamental frequency") is the sinewave your talking about. That's basically what they do in "switching power supplies". Since DC won't go through transformer windings, they simply put the DC through a switch as above to generate AC. Then they pass it through a transformer if necessary. Edison lost out on his DC power transmission to AC because they needed to raise the voltage to hundreds of thousands of volts to send it over long distance power lines. Otherwise the wires were too big and heavy. For that you need AC and transformers.

Answer 5

VoLtage versus time graph for alternative current is y=sin (theta),which is a sinusoidal shape or curve.It switches + alternance to - alternance for full period.