The man who developed one of the most profound concepts of the twentieth century is practically unknown to most engineers. He is a victim of his own law. Destined to a secure place in the engineering hall of fame, something went wrong.
His real contribution lay not merely in the discovery of the law but more in its universality and in its impact. The law itself, though inherently simple, has formed a foundation on which future generations will build.
To show the all-pervasive nature of Murphy’s work, here is a small sample of the application of the law in Electronic Engineering.
- GENERAL ENGINEERING
- A patent application will be preceded by one week by a similar application made by an independent worker.
- The more innocuous a design change appears, the further its influence will extend.
- All warranty and guarantee clauses become void upon payment of invoice.
- The necessity of making a major design change increases as the fabrication of the system approaches completion.
- Firmness of delivery dates is inversely proportional to the lightness of the schedule.
- Dimensions will always be expressed in the least usable term. Velocity for example will be expressed in furlongs per fortnight.
- An important Instruction Manual or Operating Manual will have been discarded by the Receiving Department.
- Suggestions made by the Value Analysis Group will increase costs and reduce capabilities.
- Original drawings will be mangled by the copying machine.
II. MATHEMATICS
- In any given miscalculation, the fault will never be placed if more than one person is involved.
- Any error that can creep in will. It will be in the direction that will do the most damage to the calculation.
- All constants are variable.
- In any given computation the figure that is most obviously correct will be the source of error.
- A decimal will always be misplaced.
- In a complex calculation one factor from the numerator will always move into the denominator.
III. PROTOTYPE & PRODUCTION
- Any wire cut to length will be too short.
- Tolerances will accumulate unidirectionally toward maximum difficulty of assembly.
- Identical units tested in identical conditions will not be identical in the field.
- The availability of a component is inversely proportional to the need for that component.
- If a project requires a component there will be nil units in stock.
- If a particular resistance is needed, that value will not be available. Further it cannot be developed with any available series or parallel termination.
- A dropped tool will land where it can do the most damage. (Also known as the law of selective gravitation).
- A device selected at random from a group having 99% reliability will be a member of the 1% group.
- When one connects a 3-phase line, the phase sequence will be wrong.
- A motor will rotate in the wrong direction.
- The probability of a termination being omitted from a plan or drawing is directly proportional to its importance.
- Interchangeable parts won’t.
- Probability of failure on a component assembly sub-system or system is inversely proportional to ease of repair.
- If a prototype functions perfectly, subsequent production units will malfunction.
- Components that must not and cannot be assembled improperly will be.
- A dc motor will be used on an overly sensitive range and will be wired in backwards.
- The most delicate component will drop.
- Graphic recorder will deposit more ink on humans than on paper.
- If a circuit cannot fail, it will.
- A fail-safe circuit will destroy others.
- An instantaneous power supply crowbar circuit will operate too late.
- A transistor protected by a fast acting fuse will protect the fuse by blowing first.
- A self-starting oscillator won’t.
- A crystal oscillator will oscillate at the wrong frequency – if it oscillates.
- A PnP transistor will be an NpN.
- A zero-temperature-coefficient capacitor used in a critical circuit will have a TC of -750