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Potential difference is the energy per unit charge in an electrical circuit, measured between two points. It is commonly known as voltage and can be viewed as the energy required to move a charge between points. The sign of potential difference depends on the direction of electron flow. Instruments such as voltmeters, potentiometers, oscilloscopes, and multimeters measure potential difference.
A potential difference is the energy per unit charge in an electrical circuit. The potential difference must be measured between two points because it is generally impractical to measure the electric potential of a single point. The potential difference of a point in an electrical circuit is typically realized with respect to a reference potential, such as common ground.
Potential difference is commonly known as voltage because volts are the standard unit of measure for this quantity. It is also known historically as pressure and tension. “Pressure” is an obsolete term for potential difference, but is still used to refer to potential difference in the context of vacuum tube electronics.
Voltage can also be viewed as the energy required to move a charge between points divided by the magnitude of that charge. This energy total must include both the static and dynamic energy required to move the charge. The potential difference calculation becomes more accurate as the amount of charge measured decreases.
A potential difference quantity must include a sign that depends on the direction in which the electrons are flowing. The definition of potential difference assumes that positively charged particles move towards lower voltages and negatively charged particles move towards higher voltages. This means that electrons in a circuit flow from a point of higher voltage to a point of lower voltage.
The description of potential difference often uses water as an analogy for electricity. This analogy assumes that a mechanical pump is driving water through a closed loop of pipes. The potential difference in this analogy is the difference in water pressure between two points in the circuit. Water will then flow between the two points if there is a difference in their pressure, allowing the water to do the work. Similarly, an electrical circuit can only work if there is a potential difference between two points in the circuit.
Various instruments measure the potential difference depending on their method of operation. A voltmeter has two leads, each of which connects to a point in the circuit. This device measures the voltage drop across a fixed resistor, which is proportional to the amount of volts in the circuit.
A potentiometer compares an unknown voltage to a known voltage in the circuit. An oscilloscope amplifies the voltage in the circuit, which deflects an electron beam. The amount of deflection is proportional to the voltage in the circuit. A multimeter measures various electrical quantities, including voltage.
