Why is it that if the voltage indication number is zero, the circuit of the measured part is short circuited

Why is it that if the voltage indication number is zero, the circuit of the measured part is short circuited

First of all, the voltmeter is composed of an ammeter and a resistor with a large resistance in series. After power on, a small current will flow through the resistor and the ammeter to deflect the pointer of the ammeter. The current depends on the resistance and the voltage. If the parallel part has a constant resistance, even if it is very small, the voltmeter will flow through a

Short circuit with electrical appliances (part of the circuit short circuit), how about the voltage and current on the electrical appliances?

The current will be selected through the wire. The voltage and current of the consumer is zero

Circuit short circuit, not through electrical appliances, why there is current through electrical appliances, current in the end from where the flow past, the voltage is not zero
Doesn't Ohm's law make sense

Power short circuit or electrical short circuit? It seems that you are talking about power short circuit
Ohm's law is that the wire resistance is zero in the ideal state, but it is still very large in practice
This determines that the voltage at both ends of the appliance is not exactly zero, then there is a weak current flow

As shown in the figure, the electromotive force of power supply e = 12V, internal resistance R = 1 Ω, resistance R1 = R4 = 15 Ω, R2 = R3 = 3 Ω, find: (1) when the key K is open, the potential of points a, B and D; (2) when the key K is closed, the current direction through the key K

(1) According to the meaning of the question, the main circuit current I = ER + r = 129 + 1A = 1.2A, so UAC = 12ir1 = 0.6 × 15V = 9V, because φ C = 0V, so φ a = 9V, UCB = 12ir2 = 0.6 × 3V = 1.8V, so φ B = - 1.8V, so UDC = uac-uad = (9-1.8) v = 7.2V, then φ d = 7.2V. (2) because UDC = 7.2V, φ D ＞ φ C, when k is closed, there is current through the key K, and the current direction is d → C When the switch K is off, the potential of a, B and D is respectively 9 V, 1.8 V and 7.2 v. & nbsp; & nbsp; & nbsp; & nbsp; (2) after the switch K is closed, the current through the switch flows from D to C