A person stands on an insulating mat, and you use an electric pen to test whether he has electricity. Will he be electrocuted?

As long as the pen works normally, it won't get an electric shock, but there may be a weak current passing through it.

Firstly, the working principle of the electric pen is introduced: after a certain starting voltage is applied to both ends (regardless of polarity) of the neon tube in the electric pen, neon gas is excited (electric energy input) into a plasma state, and collides with electrons to release energy (in the form of light). In fact, neon is used to repeatedly convert electric energy into light energy, and in the process, a weak current will be generated. (Neon gas is excited, and then it collides with electrons to be reduced, and then it is excited. . . If the cycle goes on, the excited neon gas and electrons walk between the positive and negative electrodes during this cycle, generating current. )

In view of the above situation: suppose you are in contact with the earth (absolute zero potential), measure the charged person with an electric pen, and the charged person has 220V from the power grid, then the neon tube reaches the starting voltage, and the charged person, neon tube, you, the earth and the power system (the whole power loop is connected to the earth somewhere) form a loop. Because the current is very weak (the safe current for human body is 0. 1A, and the electric pen seems to have several milliamps, I don't know, but I only know that it is very small), although there is current flowing through your body, neither you nor the person being charged will be electrocuted.

Pay attention to whether there is current: 1. If the voltage of the charged person does not come from the power grid or other power sources that cannot form a loop with the pen, then the pen will not form a loop when measuring electricity, and naturally it will not be charged. Suppose that a transformer (isolation transformer) circuit is suspended on the ground and contacted with a charged person. The voltage of the charged person is not the voltage to the ground at all, but the voltage of the suspension transformer. There are two circuits that have no contact points at all, so it is impossible to form a current loop when you stand on the ground and measure the voltage with an electric pen. 2. If the starting voltage (I don't know what this is, but I am sure I can distinguish the neutral wire from the normal neutral wire and live wire) is not enough, a loop cannot be formed and there is no current.