Help on Physics (1 Viewer)

[ItDunMatter]

Hello~

1) Why are Voltmeters placed in parallel whereas ammeters placed in series.

2) Why are AC used in homes instead of DC.

Thanks in advance

 

[khorne]

Well, you can think of it in several ways...Volt meters are placed in parrallel as voltage is constant in both branches of a parrallel circuit. Why is this import? well, the volt meter measures the potential "drop"/difference between two points between a resistor, so it needs to points, and as the voltage will be the same in the branch, then it can be placed in parallel.

Current on the other hand is the same in any location in a (series) circuit, thus the ammeter is placed in a location so the current can just pass through, thus being measured.

2) This kind of ties with the battle between Edison and Westinghouse. The voltage in a DC circuit decreases with the length of the wire, so by the time the electricity reached your house from the power station, the voltage would be very low (or there would need to be a lot of repeaters). AC is used because the voltage doesn't decrease over long distances, and transformers can be used to alter the voltage (step it up/down), so high voltage can travel from the power plant and it can gradually be decreased until it arrives to your street/house etc.

 

[Aquawhite]

Well, you can think of it in several ways...Volt meters are placed in parrallel as voltage is constant in both branches of a parrallel circuit. Why is this import? well, the volt meter measures the potential "drop"/difference between two points between a resistor, so it needs to points, and as the voltage will be the same in the branch, then it can be placed in parallel.

Current on the other hand is the same in any location in a (series) circuit, thus the ammeter is placed in a location so the current can just pass through, thus being measured.

2) This kind of ties with the battle between Edison and Westinghouse. The voltage in a DC circuit decreases with the length of the wire, so by the time the electricity reached your house from the power station, the voltage would be very low (or there would need to be a lot of repeaters). AC is used because the voltage doesn't decrease over long distances, and transformers can be used to alter the voltage (step it up/down), so high voltage can travel from the power plant and it can gradually be decreased until it arrives to your street/house etc.

+1 exactly what I could explain it as.

 

[LeagueofLegends]

Haha ur shit!

 

[cutemouse]

1) Why are Voltmeters placed in parallel whereas ammeters placed in series.

It is worth noting that the structures of ammeters and voltmeters are identical. Volmeters just have a resistor connected in series within them.

So if a voltmeter is connected in series in a circuit then not much current would pass it, and so devices (eg. light globe) on the circuit would not be able to be powered. So it is connected in in parallel.

Ammeters on the other hand do not have much resistance, so if you connect them in parallel then alot of current will flow (current flows in the path with least resistance), and not through the load/device. So they need to be connected in series to measure the current being supplied to the load/device.

A good analogy is a water circuit. Consider the pump to be the source and a resistor be anything that obstructs the flow of water (eg. a narrower pipe than the rest of the circuit). A voltmeter would measure the pressure 'difference' in pressure on either side of the 'resistor' and the ammeter would measure how much water (analogous to current) flowing.

2) Why are AC used in homes instead of DC.

DC voltages are difficult to step up and step down, whereas AC is easier to step up and step down (using transformers). Also, it is easier to convert AC in DC, than DC into AC, which is required for household specific household appliances.

Power loss = I^2 * R, so we need to reduce I to reduce power loss.

Now P=IV, so if we are going to decrease I, we need to increase V if we're going to maintain the same amount of power being transmitted. This is done by stepping up voltages. Hence why AC is used.

But if DC could be transformed easily then it could well be a better way to transmit electricity for various reasons that you will study in Year 12 HSC Physics.