UPSC Prelims 2005 · General Studies
Question 18: Science and Technology
What is the order of magnitude of electric resistance of the human body (dry)?
AnswerThe answer is (b).
The key takes the resistance of the dry human body as of the order of 10⁴ ohm, tens of thousands of ohms. Dry skin offers high resistance, while wet or sweaty skin drops to around a thousand ohm or less, which is why electric shocks are far more dangerous with wet hands. Remember: dry skin, thousands to lakhs of ohm; wet skin, about 10³ ohm.
Why each option is right or wrong
- (a) 10² ohm is far below any usual figure for dry skin.
- (b) Given answer: the order of 10⁴ ohm.
- (c) 10⁶ ohm is higher than usual dry-skin figures.
- (d) 10⁸ ohm is far too high for the human body.
Worth knowing: Textbooks quote dry-skin resistance anywhere from about 10³ to 10⁵ ohm, so the choice of 10⁴ depends on the source the key follows.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2005, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.