Glossary – O

Ohm: Unit of measure for resistance(Q). The value of the ohm has been internationally agreed to as being the amount of electrical resistance that a column of mercury, 106.3 centimeters long, 1 millimeter square, at OOC, will present to current flow in a circuit. The mercury has a mass of 14.4521 grams. A common definition is that when 1 volt is applied to a circuit, and 1 ampere flows in the circuit, then 1 ohm of resistance is present


Ohm’s Law: The relationship that exists among voltage, current, and resistance in a circuit. E = I x R. For AC circuits, the resistance is replaced by the impedance (Z) of the circuit.


Open Circuit: Circuit broken or the load is removed. Load resistance is undefined in value.


Osmosis: Movement of a solvent through a semi-permeable membrane into a solution of higher solute concentration. The result tends to equalize the concentration of solute on the two sides of the membranes.


Outside to Inside Temperature Difference (OITD): The temperature of the hull exterior as compared to the temperature of the enclosed interior of a vessel.


Overcurrent Protector: A device such as a fuse or circuit breaker that removes the load from the power source when a predetermined level of current is drawn by the circuit.


Overload Protector: A temperature detecting device built into a motor circuit that protects the motor for the power source if the temperature rise becomes excessive.