- Ohm's Law
- (n.f.) In the case of a resistor, the voltage is proportional to the current intensity. U = R×I with U in volts, I in amperes, and R in ohms. The voltage (in volts) across a resistor is equal to the product of the current intensity (in amperes) passing through it and its resistance (in ohms).
- Ohm, Georg Simon (1787 or 1789-1854)
- German physicist. In 1827, he discovered a fundamental law of electricity, which now bears his name. He precisely defined the concepts of resistance and resistivity, as well as their inverses.
- Ohm
- (n.) Legal unit of electrical resistance (Symbol Ω).
- Ohmic Conductor
- (n.) Two-terminal component whose voltage is proportional to the current intensity.
- Ohmmeter
- (n.) Device for measuring electrical resistance. It is connected directly to the receiver (generally a resistor).
- Opaque
- (adj.) Describes an object that does not allow light to pass through.
- Open Circuit
- (n.) Circuit in which no electrical current flows and often containing an open switch.
- Orbit
- (n.) Path described by the center of a celestial body (a planet, a satellite, etc.) during its movement.
- Ordered State
- (n.) A state of matter where molecules are arranged in a regular manner.
- Oscillogram
- (n.) Image that appears on the screen of an oscilloscope.
- Oscilloscope
- (n.) Imaging device that visualizes the variations of a voltage over time. It allows determining the maximum value of the voltage and its period T. The maximum voltage is equal to the product of the maximum deviation and the vertical sensitivity. The period T is equal to the product of the length of the elementary pattern and the sweep speed.
- Over-Current
- (n.) Current intensity higher than the nominal intensity of an electrical receiver, which can damage or even destroy it. A lamp with over-current shines very brightly and can burn out quickly.
- Over-Voltage
- (n.) Voltage higher than the nominal voltage of an electrical receiver, which can damage or even destroy it. A lamp with over-voltage shines very brightly and can burn out quickly.
- Oxidizing Agent
- (n.) Substance necessary for fuel to burn. Oxygen is a good oxidizing agent.
- Oxygen
- (n.) Atom with atomic number Z equal to 8. It consists of 8 electrons orbiting a nucleus containing 8 protons and 8 neutrons. Symbol O. Its model is a red sphere.
- Ozone
- (n.) Bluish gas with a characteristic pungent odor, formula O3. The boiling point of ozone is -112°C. Its melting point is -250°C. Unstable at ordinary temperatures, it tends to slowly transform into dioxygen. It forms either from dioxygen under the action of an electric spark or from nitrogen oxides and hydrocarbons present in the air. It is dangerous at low altitudes. It can cause asthma attacks and bronchitis and is harmful to plants and many materials. In the stratosphere, however, it indirectly plays a protective role against excess UV radiation that could reach the Earth's surface.