Why do we not get an electric shock while using the domestic electricity tester (the one that looks like a screw driver)? Can this tester be used on a surface that has high-voltage electricity (> 240 volts)?

Before I can answer this question, let me show you how a tester functions.

A tester is basically the equivalent of a light bulb with an extremely high resistance. When using the tester, you place the screw driver’s end into the terminal that is ‘live’ of the socket. You then place your finger to the metal top of the tester, while sitting in the middle of the floor. What you’re doing is creating an electrical circuit connecting the live terminal of the tester, and finally your physique to ground. This is why electricity flows through your body through the AC plug in the wall to the ground , making the tester’s light bulb to glow.

What’s keeping you safe is the resistance in the series of the tester. This resistor limits the amount of electrical current that flows into your body, to levels, but not enough to cause an electric shock.

The testers are utilized mostly to identify live wires that are present in the domestic AC circuitry (240V in India). They shouldn’t be used to detect higher voltages. The current that flows through your body could be more intense and could prove dangerous.

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