What is "load line"

Load \Load\ (l[=o]d), n. [OE. lode load, way; properly the same word as lode, but confused with lade, load, v. See Lade, Lead, v., Lode.]

1. A burden; that which is laid on or put in anything for conveyance; that which is borne or sustained; a weight; as, a heavy load.

   He might such a load To town with his ass carry.
   --Gower.

2. The quantity which can be carried or drawn in some specified way; the contents of a cart, barrow, or vessel; that which will constitute a cargo; lading.

3. That which burdens, oppresses, or grieves the mind or spirits; as, a load of care. `` A . . . load of guilt.''
   --Ray. `` Our life's a load.''
   --Dryden.

4. A particular measure for certain articles, being as much as may be carried at one time by the conveyance commonly used for the article measured; as, a load of wood; a load of hay; specifically, five quarters.

5. The charge of a firearm; as, a load of powder.

6. Weight or violence of blows. [Obs.]
   --Milton.

7. (Mach.) The work done by a steam engine or other prime mover when working.

8. The amount of work that a person, group, or machine is assigned to perform; as, the boss distributed the load evenly among his employees.

9. (Elec.) The device or devices that consume power from a power supply.

10. (Engineering) The weight or force that a structural support bears or is designed to bear; the object that creates that force.

    Load line, or Load water line (Naut.), the line on the outside of a vessel indicating the depth to which it sinks in the water when loaded.

    Syn: Burden; lading; weight; cargo. See Burden.

n. The line on the outside of a vessel indicating the depth to which it sinks in the water when loaded.

n. waterlines to show the level the water should reach when the ship is properly loaded [syn: Plimsoll line, Plimsoll mark, Plimsoll]

Load line may refer to:

• Ship's load line, related to ship construction
• Load line (electronics), a method of determining operating points in circuits with non-linear elements. This method was often used with vacuum tubes

A load line is used in graphical analysis of nonlinear electronic circuits, representing the constraint other parts of the circuit place on a non-linear device, like a diode or transistor. It is usually drawn on a graph of the current vs the voltage in the nonlinear device, called the device's characteristic curve. A load line, usually a straight line, represents the response of the linear part of the circuit, connected to the nonlinear device in question. The points where the characteristic curve and the load line intersect are the possible operating point(s) ( Q points) of the circuit; at these points the current and voltage parameters of both parts of the circuit match.

The example at right shows how a load line is used to determine the current and voltage in a simple diode circuit. The diode, a nonlinear device, is in series with a linear circuit consisting of a resistor, R and a voltage source, V. The characteristic curve (curved line), representing the current I through the diode for any given voltage across the diode V, is an exponential curve. The load line (diagonal line) represents the relationship between current and voltage due to Kirchhoff's voltage law applied to the resistor and voltage source, is

V = V − IR 
Since the current going through the three elements in series must be the same, and the voltage at the terminals of the diode must be the same, the operating point of the circuit will be at the intersection of the curve with the load line.

In a BJT circuit, the BJT has a different current-voltage (I-V) characteristic depending on the base current. Placing a series of these curves on the graph shows how the base current will affect the operating point of the circuit.