Posted By AMJAD AL ATA Hi all, Does the the use of reduced/low voltage system prevent the risk of electirc shock or reduce the severity of the electric shock? Regards Amjad

Posted By AMJAD AL ATA Hi The Toecap, The current amount is which will casue the electric shock by passing body to earth is based on the the voltage & the resistance (I = V/R) thus the more the V the more the I ((if R is constant)). Then my question again, Does the use of reduced voltage systems reduce the liklihood of shock or the severity of shock? (for me it will reduce the severity, but the topic infront of me says it reduce the liklihood of being shocked) Regards Amjad

Posted By Calum R Cameron Amjad- the answer to your question is YES. I am an ex-electrician so here goes.....Voltage and current are inversely proportional therefore if you reduce the voltage by half you will double the current flow for a given load-i.e. 1000w=100v x10a or 100a x10v. this is a very simplified view and does not take account of load type (capacitive or inductive). Shock severity is determined by a number of factors not least the resistance of human skin in that very dry hard skin will provide more resistance than wet skin so the current flow would be reduced. Other factors include contact point-current path`- individual susceptability and atmospheric conditions such as humidity. Bottom line is-reduce the voltage - reduce the risk. Oh and by the way-there is no such term as "amperage". Cheers

Posted By AMJAD AL ATA Thanks to all who respond. Calum, it is clear now (really i confused by this, moreover i am under the pressure of comming nebosh cert. exam) Regards Amjad

Posted By Tom Doyle Protection from electric shock. This question involves more than the simple application of ohms law in order to achive compliance. For information regarding protection from electric shock refer to IEC 60204-1 Section 6. Canadian Electrician Cheers Tom

Posted By David J Jones Amjad, Whilst agreeing with the other postings in respect of Ohms Law et al, should you be asked for an example in your NEBOSH, you could usefully state the use of a mains powered electric tool which is fed from a step-down transformer (depends on the supply voltage where you are) which is centre-tapped to earth. This then would give, in the UK, mains at 240v, stepped down to 115v with the transformer, this being centre-tapped to earth would give an effective and far less lethal, actual voltage of around 55 - 60 volts if either the live or return conductors were touched.

Posted By Malcolm Fryer Amjad I have a degree of fear in trying to assist you on this one as I am not as expert as some of the other contributors but current is a major issue here. Firstly remember you are working towards a General Certificate examination and this does not demand the high level of expertise offered to you in order to answer it. In my judgement for this exam it will be adequate to state that reduced/low voltage systems prevent or reduce the risk and severity of electric shock. To get back to your original post GENERALLY Low voltage is an indication of a system that runs below 50 volts and reduced voltage is one that runs at or below 110 volts. It should be noted that often the 110 volt systems are centre tapped to earth resulting in a lower potential difference (voltage) of 55 volts. There are many factors that effect the likelihood of an electrical shock (apart from the human ones) and this will typically involve the individual’s health, the variable resistance of the human body which is effected by moisture in the environment, and what is being worn that could interrupt the circuit. The severity of the shock will be affected by many factors including human variation, body resistance and especially the electrical path. One of the worst scenarios is holding a faulty electrical device in your hand which then makes a circuit across your chest where the major organs including the heart are sited. There is a particular issue with hand held appliances in that when shocked the body goes into muscular spasm and most people literally cannot let go of a gripped item at between 10-25 mA. I suspect that despite the above you will want to know more and I would suggest that you look at the following. http://www.geaps.com/proceedings/2003/nicewicz.cfm which whilst not a UK site offers some excellent guidance on this issue and http://www.listenhear.co.uk/ohms_law.htm Which states. A steady increase in voltage, in a circuit with constant resistance, produces a linear rise in current. A steady increase in resistance, in a circuit with constant voltage produces a progressively weaker current. Good luck with your exam and remember they are not looking for an in depth answer for the NEBOSH General Certificate Malcolm