Most of us fear an electric shock, yet we know little about what is safe and what is not when we handle electricity. For example, most of the time we are cautious about handling electrical devices which seem to be complicated in structure, but do not worry about turning off the electricity with a wet hand. Maybe you don’t mind placing your radio or the hair drier on the wet surface in the bathroom.
Body fluids are not as good conductors as metals. Their resistance is much higher. For example, a current of microamperes flowing directly through the heart can bring about death. On the other hand, a current of 100 to 200 microamperes through electrodes on the chest triggers the regular beating of the heart, after the heart has stopped. The reason for such a big difference in the effects of the two values is that the first current is sent directly to the heart and the second has to pass through the fluids of the body, which have a greater resistance.
As you can see, in an electric shock, it is the current that matters, not the voltage. One thing about the injuries associated with electric shocks is that, most of the time, they arise from involuntary body movements in response to the current. For example, the current may cause you to lose your balance and to fall off a ladder. Sometimes, the victim freezes with the current, maybe because some muscles are paralyzed for a moment, and he cannot let go of the thing he is holding. As he keeps holding the object, there will be more current sent through the body.
One other thing about electric shocks is the burns they cause. When the skin burns, a low resistance path is established for the current and now the current can cause more damage.
Some electrical appliances require earthing. With these appliances, if the insulation becomes frayed, the leakage is carried to the ground, without doing any harm. Most of the time, people use extension cables without the earthing or make incorrect connections. It is not safe to do so.
Always use the proper extensions and connections. One other mistake made by most people is to wind thick wires around fuses, to prevent the fuse from blowing frequently. The fuses are there for safety, to prevent the overloading of the current. If they do not blow, then the excess current may cause damage to the electrical appliances or even cause a fire. Briefly, it is not safe to play with electricity. Never forget that your body resistance is lowered greatly when it is wet. Always be careful with electricity, but never panic. If you see someone caught up in an electric shock, before you reach out to rescue him, go to the fuse box and shut off the circuit at the main inlet.
A. What do the following refer to?
1. ‘they’ (line 25): 2. ‘if (line 39):
B. Mark the best choice. 1. Line 3, ‘cautious’ means . a) ignorant b) curious c) worried d) careful
2. Line 11, ‘triggers’ means . a) increases b) starts c) stops d) decreases
3. Line 21, ‘freezes’ means . a) becomes very cold c) holds on tightly b) is unable to move d) becomes electrified
4. Line 29, ‘frayed’ means . a) worn out b) harmful c) renewed d) overloaded
5. We don’t usually worry about turning off the electricity with a wet hand because we .
a) know that it is safe to do so b) don’t mind handling simple electrical devices c) don’t fear an electric shock d) know a great deal about electricity
6. Injuries related to electric shocks are mostly due to the . a) involuntary response of the body to the shock b) type of appliance in which there was a leak c) voltage of the electric shock d) Both (b) and (c).
7. Lines 31-32, ‘It is not safe to do so’ means it is not safe to . a) use extension cables without earthing b) carry the leakage to the ground c) make incorrect connections d) Both (a) and (c).
1. Why does a low voltage electric current applied directly through the heart cause death while a higher one applied through electrodes on the chest does not?
2. Why does burnt skin enable the current to cause more damage?
3. What kind of misuse of electricity may cause fire?