basic circuit convention 1

[Leclerc]

Hi! No circuit engineer, me - as you will discover. I need to understand some basic circuit conventions upon which I may build, and I would be grateful if someone could answer the following questions.

1. Is it convention to draw circuits with the V0 (-ve) connector at the bottom of the diagram, with the V (+ve) connector at the top, or vice versa?

2. Voltage drops from a high voltage to a lower voltage, but is it convention that the current flows in this direction? Would any arrows describing the flow of electricity (current) be from a high to a lower voltage?

These may seem trivial, but I have seen contradictory evidence in books/ periodicals of all ages, and i want to get this matter nailed once and for all.

PS I have read a previous thread which seems to partly answer these questions, but the subject matter, dealing as it did with current source and current sink, confused me.

thanks in anticipation : Leclerc

 

[logbook]

Hi Leclerc,

you may well find that the conventions are different according to the industry you are in and the nature of the circuit. 3-phase circuits, for example, would be drawn quite differently to low voltage DC circuits as found inside instrumentation.

I will answer for the instrumentation camp.

1) Steady voltage supplies (DC) would be more positive at the top of the diagram. Going down the page would be +15V, +12V, +5V, 0V, -5V, -12V, -15V and so forth. Often there is a space between the number and the units "+15 V", which is the more correct form, although many CAD packages would be unhappy with this format.

2) Conventional current always flows from positive to negative. On a circuit diagram the current flows "downhill". Note that signals can, and often do, flow "uphill". A conventional diode symbol shows the direction of conventional current flow by the arrow shape of its body.

 

[BrianG]

Hi Leclerc,

One further point to add to those from Logbook is that for electronic circuits the convention is to have input signal arriving at the left side of the diagram and output signals leaving on the right of the diagram.