–D. L. Klipstein
Murphy’s Law, in its simplest form, states that “If anything can go wrong, it will.” Or to state it in more exact mathematical form:
where ↵ is the mathematical symbol for “hardly ever.”
To show the all-pervasive nature of Murphy’s work, the author offers a few applications of the law to the electronic engineering industry.
1. Any error that can creep in, will. It will be in the direction that will do the most damage to calculations.
2. All constants are variables.
3. In a complicated calculation, one factor from the numerator will always move into the denominator, or conversely.
4. A patent application will be preceeded by one week by a similar application made by an independent worker.
5. The more innocuous a design chage appears, the further its influence will extend.
6. All warranty and guarantee clauses become void on payment of invoice.
7. An important Instruction Manual or Operating Manual will have been discarded by the Receiving Department.
Prototyping and production
8. Any wire cut to length will be too short.
9. Tolerances will accumulate unidirectionally towards maximum difficulty of assembly.
10. Identical units tested under identical conditions will not be identical in the field.
11. If a project requires n components, there will be (n – 1) units in stock.
12. A dropped tool will land where it can do most damage; the most delicate component will be the one to drop. (Also known as the principle of selective gravity.)
13. A device selected at random from a group having 99 percent reliability will be a member of the 1 percent group.
14. A transistor protected by a fast-acting fuse will protect the fuse by blowing first.
15. A purchased component or instrument will meet its specifications long enough, and only long enough, to pass Incoming Inspection.
16. After an access cover has been secured by 16 hold-down screws, it will be discovered that the gasket has been omitted.
Condensed from “The Contribution of Edsel Murphy to the Understanding of Behaviour in Inanimate Objects,” in EEE: The Magazine of Circuit Design, August 1967.