When is voltage negative in a circuit

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These cookies do not store any personal information. Non-necessary Non-necessary. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. Remember — a battery being 9V means the plus terminal is 9V higher than the minus terminal. What happens if we connect the plus of the second battery to the minus of the first one i.

Nothing really happens with the batteries. Since the minus is 9V lower than the plus, and since the plus is connected to ground, the minus would have to be minus 9V.

When we do this, it looks as if we are talking about voltage at a single point, but we are actually expressing the voltage at that point relative to some rather arbitrary reference voltage which is taken to be zero.

This reference voltage is called ground. The above interpretation of polarity is only correct if the voltage V AB is a positive number. If V AB is a negative number, the voltage at terminal A is higher than the voltage at terminal B by a negative amount—this is equivalent to saying that the voltage at terminal A is lower than the voltage at terminal B.

Note: The overall idea is similar to that used when we define altitudes in geography. Altitudes are, by common agreement, specified relative to sea level. Altitudes can be either positive above sea level or negative below sea level , just as voltages can be either positive or negative relative to ground.

Ground, in electrical circuit schematics, is denoted by one of the symbols shown in Fig. Although all three symbols define a zero volt level for any other voltages on the schematic, they do not mean the same thing. Earth ground, Fig. Earth ground on a circuit schematic implies that there is some physical connection between the circuit and the earth.

Signal ground, Fig. On circuit schematics, signal ground is indicated by the symbol shown in Fig. We will discuss more details about the differences among various grounds in a different project. Voltage differences are usually measured with a voltmeter. A voltmeter will have two terminals, or leads, which are connected to the two points in our circuit across where we want to measure voltage.

For example, suppose that we want to measure the voltage across circuit 2 V 2 shown in Fig. We simply connect the terminals of the voltmeter to the terminals of circuit 2 in order to measure the voltage across circuit 2, as shown in Fig. Generally, voltmeters are implemented as one function of a digital multimeter, or DMM. Work is measured in joules per unit of charge which is required to create a continuous flow of electrons.

A 9-volt battery, for example, does 9 joules of work per coulomb of charge. The battery performs work, which is divided among the various components in the system. While a battery provides energy for moving the charge, components consume energy. This change results in a voltage drop.

The more resistance in a circuit, the more work or voltage is required to move the charge as current flow. Polarity reflects how the current flows from positive to negative within a circuit.

While current flows from the positive to the negative terminal, electrons flow from a negative to a positive direction.