terminal voltage

(noun)

The voltage output of a device measured across its terminals.

Related Terms

Examples of terminal voltage in the following topics:

  • EMF and Terminal Voltage

    • The output, or terminal voltage of a voltage source such as a battery, depends on its electromotive force and its internal resistance.
    • The voltage output of a device is measured across its terminals and is called its terminal voltage V.
    • Terminal voltage is given by the equation:
    • The larger the current, the smaller the terminal voltage.
    • (Note that the script E stands for emf. ) Also shown are the output terminals across which the terminal voltage V is measured.

  • The Battery

    • The electrical driving force across the terminals of a cell is known as the terminal voltage (difference) and is measured in volts.
    • The voltage of a battery is synonymous with its electromotive force, or emf.
    • Voltage is not the same as energy.
    • Voltage is the energy per unit charge.
    • Thus a motorcycle battery and a car battery can both have the same voltage (more precisely, the same potential difference between battery terminals), yet one stores much more energy than the other.

  • Null Measurements

    • When measuring the EMF of a battery and connecting the battery directly to a standard voltmeter, as shown in , the actual quantity measured is the terminal voltage V.
    • A potentiometer is a null measurement device for measuring potentials (voltages).
    • A voltage source is connected to resistor R, passing a constant current through it.
    • Note that emfx opposes the other voltage source.
    • An analog voltmeter attached to a battery draws a small but nonzero current and measures a terminal voltage that differs from the EMF of the battery.

  • Peripheral Motor Endings

    • A neuromuscular junction exists between the axon terminal and the motor end plate of a muscle fiber where neurotransmitters are released.
    • A neuromuscular junction is the synapse or junction of the axon terminal of a motor neuron with the motor end plate, as shown in Figures 1 and 2.
    • Upon the arrival of an action potential at the presynaptic neuron terminal, voltage-dependent calcium channels open and Ca2+ ions flow from the extracellular fluid into the presynaptic neuron's cytosol.
    • The depolarization activates L-type voltage-dependent calcium channels (dihydropyridine receptors) in the T-tubule membrane, which are in close proximity to calcium-release channels (ryanodine receptors) in the adjacent sarcoplasmic reticulum.
    • T is the axon terminal and M is the muscle fiber.

  • Voltmeters and Ammeters

    • Voltmeters and ammeters are used to measure voltage and current, respectively.
    • Voltmeters and ammeters measure the voltage and current, respectively, of a circuit.
    • The value of R is determined by the maximum voltage that will be measured.
    • Since R and r are in parallel, the voltage across them is the same.
    • Note that terminal voltage is measured between points a and b.

  • Sources of EMF

    • Electromotive force (EMF) is the voltage voltage generated by a battery or by the magnetic force according to Faraday's Law of Induction.
    • Formally, EMF is classified as the external work expended per unit of charge to produce an electric potential difference across two open-circuited terminals.
    • When current flows, however, the voltage across the terminals of the source of EMF is no longer the open-circuit value, due to voltage drops inside the device due to its internal resistance.
    • Again the EMF is countered by the electrical voltage due to charge separation.
    • If a load is attached, this voltage can drive a current.

  • Humans and Electric Hazards

    • A short circuit is a low-resistance path between terminals of a voltage source.
    • Such an undesired contact with a high voltage is called a short.
    • Since current is proportional to voltage when resistance is fixed (Ohm's law), high voltage is an indirect risk for producing higher currents.
    • Very high voltage (over about 600 volts): This poses an additional risk beyond the simple ability of high voltage to cause high current at a fixed resistance.
    • A short circuit is an undesired low-resistance path across a voltage source.

  • Synaptic Transmission

    • When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated Na+ channels.
    • This depolarization causes voltage-gated Ca2+ channels to open.
    • Calcium is quickly removed from the terminal.
    • The neurotransmitter termination can occur in three ways.
    • When the presynaptic membrane is depolarized, voltage-gated Ca2+ channels open and allow Ca2+ to enter the cell.

  • Nerve Impulse Transmission within a Neuron: Action Potential

    • Transmission of a signal within a neuron (in one direction only, from dendrite to axon terminal) is carried out by the opening and closing of voltage-gated ion channels, which cause a brief reversal of the resting membrane potential to create an action potential .
    • Once the signal reaches the axon terminal, it stimulates other neurons.
    • At the same time, voltage-gated K+ channels open, allowing K+ to leave the cell.
    • For an action potential to communicate information to another neuron, it must travel along the axon and reach the axon terminals where it can initiate neurotransmitter release .
    • Nodes contain voltage-gated K+ and Na+ channels.

  • Ohm's Law

    • The phrase IR drop is often used for this voltage.
    • Voltage is similar to fluid pressure.
    • If voltage is forced to some value V, then that voltage V divided by measured current I will equal R.
    • A simple electric circuit in which a closed path for current to flow is supplied by conductors (usually metal wires) connecting a load to the terminals of a battery, represented by the red parallel lines.
    • The voltage drop across a resistor in a simple circuit equals the voltage output of the battery.