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Stuck with current & resistance

iamspiderman

(edited 7 years ago)

Reply 1

uberteknik

Original post by iamspiderman

So far for question b)i) I've said that outside you are more prone to an electric shock as it may rain and the electrical appliances may get wet and if you're standing on a work platform such as a ladder or scaffolding them you could fall from the electric shock ..

I need some help , I need to relate it to the image in the question

Those are OK answers (especially the getting wet one) but it's not the whole story and what the question is primarily trying to get at.

The diagram gives a big hint in the wording: resistance comes up time and again and it's this parameter together with voltage that determines how much current will flow between the high voltage source (live mains voltage) and the lower 0V 'Earth' potential. Voltage x Current = Power and the more power there is, the greater the chance of both skin burns from high current flow and electrical shock affecting the natural electrical activity of the brain controlling the heart muscles (seizure), hand muscles which may tighten grip around a live cable etc. (A few tens of milliamps and around 50 V d.c. or 100V a.c. is enough to kill).

You need to know what that word 'Earth' (sometimes referred to as ground) means in electrical terms. i.e. it's the reference voltage potential for that domestic mains generated voltage and electrical-earth provides an infinite sink for current.

The earth wire in a domestic mains supply is literally a conductor rod driven several feet into the ground. It's where electric current naturally wants to flow to.

So the closer the gardener is to contact with 'earth' (i.e. outside) the less resistance there is for the path of the high voltage current to flow down into the earth. Via the gardener!

Hence rubber boots to insulate the gardener from the ground should he come into contact with a live conductor in a damp/moist/wet environment like outside. The boots are there to provide a very high resistance path to earth and hence little or no current will flow through him/her. Rubber boots have the same effect as the high resistance dry environment indoor floor covering.

(edited 9 years ago)

Reply 2

Joinedup

I can think of two things

1. likelihood of there being water around in bathrooms - possibly providing low resistance current paths to earth
2. exposed earthed metalwork - taps, metal bathtubs etc.