Final answer:
You feel shocks when touching metallic objects due to the rapid discharge of static electricity accumulated in your body. On dry days, static charges build up more easily due to low humidity, making shocks more common. To mitigate the shock, you can use a wider grip when touching metal objects in low humidity environments.
Step-by-step explanation:
You sometimes feel a shock when you touch metallic objects because of a phenomenon known as static electricity. This sensation is due to the discharge of accumulated excess charge in your body, often caused by friction between your shoes and the carpet (or other surfaces). As you walk, your shoes gather more and more electrons, creating an imbalance of charge. When you touch a metallic object, which is a good conductor, the excess electrons rapidly jump to the metal, leading to a shock.
These shocks are particularly common on a dry day because low humidity allows static charges to build up more easily. Dry air does not conduct electricity well, so the charges that you accumulate as you move around are not dissipated by the moisture in the air. Consequently, the potential difference between your charged body and a grounded object, like a metal doorknob, is greater, leading to a more noticeable shock.
Moreover, safety measures take into account the effects of electrical currents on the human body. Small currents (< 5 mA) are technically harmless and below our threshold of sensation. However, larger currents can cause involuntary muscle contractions, and in severe cases, the 'can't let go' effect, where muscles in the hand involuntarily clench around an electrified object, making the shock potentially dangerous.
Lastly, in regions with low humidity, it is advised to use a special grip when touching metal objects, where you place as much of your hand on the object as possible. This technique spreads out the discharged electrons over a larger area of your hand, leading to a reduced sensation of shock.