Murphy's Law.

General Engineering.

1. The need for major design changes, are discovered as the unit nears completion.

2. Firmness of delivery dates are inversely proportional to the tightness of the schedule.

3. Dimensions will always be expressed in the least useable term. Velosity for instance, will be expressed in furlongs per fortnight.

4. Instruction Manuals will be lost on delivery of the units.

5. Original Circuit Diagrams will be destroyed by the Photocopying Machine.


1. In any given calculation, the fault will never be found, if more than one person is involved.

2. Any error that can creep in will, and it will be in the direction that will do the most damage to the calculation.

3. All Constants are variables.

4. In any given computation, the figure that is obviously correct will be the source of the error.

5. A Decimal point will alway be misplaced.

Prototypes and Production.

1. Any wire cut to length - will be short.

2. Identical Circuits. Tested under identical conditions will NOT be identical in practice.

3. The availability of a component is inversely proportional to the need for the component.

4. If a project requires "N" components, there will be "N-1" in stock.

5. If a particular Resistance is needed, that value will not be available, furthermore, it connot be made up of series/parallel combinations.

6. A dropped tool, will always fall where it will do the most damage. (Also known as the selective law of gravitation).

7. If you connect a Three Phase Line, the Phase sequence will be wrong. 8. A Motor will always rotate in the wrong direction.

9. Interchangeable parts - Won't !.

10. Components that must not (and cannot) be assembled wrong - Will be.

11. A DC Meter will always be on an overly sensitive range, and will be wired into circuit in the wrong direction.

12. If a circuit cannot fail, it will.

13. A Failsafe Circuit will destroy others.

14. A Transistor protected by a fast acting fuse, will protect the fuse by blowing first.

15. A Self Starting Oscillator - wont start.

16. A Crystal Oscillator will oscillate at the wrong frequency, If it works at all.

17. If a PNP Transistor is required. Only NPN will be in stock.

18. In any given estimate, the cost of the equipment will exceed the estimate by a factor of 3.

In Practice - Murphy's Law supersedes Ohms Law.

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