Why do electrical devices increase output when turned clockwise?

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Offline syhprum

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On most electrical devices I have to increase the output sound, brightness, contrast etc the controls must be turned 'clockwise' (top to right) but on power controlling devices such as gas taps, cooker controls, water taps etc the reverse applies.
Does this apply to large devices, if I want to let more water thru the Grand Coulee dam or raise the control rods on a nuclear reactor which way do I turn the handle?.
Did this ambiguity in any way contribute to the problem at Chernobyl!.
 
« Last Edit: 01/05/2009 22:44:26 by chris »
syhprum

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Offline Bored chemist

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The pressure regulators on gas cylinders often (in my experienece) go the other way.
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Offline graham.d

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Good point. Mechanical devices (such as valves or taps for example) usually have a convention of opening or unscrewing which is anti-clockwise. Electrical controls have a convention of clockwise for increasing something, be it volume or brightness etc.

I think this convention probably arose from screw threads, in the case of mechanical devices. They tend to be in the way described. For a valve or tap the action of rotating is to effectively unscrew a plunger which is blocking a path of a fluid. Modern valves and taps can operate on different principles but the convention has remained; although I have got a sink fitted with (ceramic) taps so that the hot tap works this way and the cold the other - and I keep turning the damn thing the wrong way!

The convention of increasing (electrical knobs) being clockwise may be related to clocks going this way - I'm not sure.

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Offline techmind

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And just to confuse you, while domestic water taps usually go anticlockwise to increase flow, various "stopcocks" where the water enters the premesis go the other way (at least in the UK) for some reason.

You are supposed to turn these stopcocks fully on, then back half a turn and leave them like that. If/when someone comes to turn them off, rather than forcing the tap the wrong way, they should find it goes half a turn before stopping so they get a hint.
"It has been said that the primary function of schools is to impart enough facts to make children stop asking questions. Some, with whom the schools do not succeed, become scientists." - Schmidt-Nielsen "Memoirs of a curious scientist"

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Offline graham.d

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Goodness, I've never come across those. All the stopcocks I have seen have been conventional. Good idea about leaving them not quite fully open. Particularly as these things get very stiff as they are not used often.

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lyner

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There is a similar confusion with switch terminology. An open switch / open circuit does not let current pass but  open taps  and open roads do permit flow. Close a switch and it lets current pass but close a tap or road . . . . .