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If n is an even superperfect number, then n must be a power of 2, 2 k, such that 2 k+1 − 1 is a Mersenne prime. [1] [2] It is not known whether there are any odd superperfect numbers. An odd superperfect number n would have to be a square number such that either n or σ(n) is divisible by at least three distinct primes. [2]
The electric part of such a meter is an electromagnetic measuring instrument which is connected to the anode and cathode of a selenium photo cell that produces more or less electric power when exposed to more or less light. The optical part of such a meter is a window in front of the photo cell's light-sensitive side.
Battery tester. A battery tester is an electronic device intended for testing the state of an electric battery, going from a simple device for testing the charge actually present in the cells and/or its voltage output, to a more comprehensive testing of the battery's condition, namely its capacity for accumulating charge and any possible flaws affecting the battery's performance and security.
An optical power meter (OPM) is a device used to measure the power in an optical signal. The term usually refers to a device for testing average power in fiber optic systems. Other general purpose light power measuring devices are usually called radiometers , photometers , laser power meters (can be photodiode sensors or thermopile laser ...
The useful power of an engine with shaft power output can be calculated using a dynamometer to measure torque and rotational speed, with maximum power reached when torque multiplied by rotational speed is a maximum. For jet engines the useful power is equal to the flight speed of the aircraft multiplied by the force, known as net thrust ...
Cell balancing in a 5-cell battery, where the fifth cell has a lower capacity. Legend: A , Case where cells are unbalanced; B , Case where cells 3 and 5 and significantly discharged; C , Case where cells 2 and 5 and significantly over-charged; D , Case where battery is being charged with a passive balancer working on cells 2 and 5.
In practice the conductivity cell is calibrated by using solutions of known specific resistance ρ*, so the individual quantities l and A need not be known precisely, but only their ratio. [11] If the resistance of the calibration solution is R *, a cell constant, defined as the ratio of l and A (C = l ⁄ A), is derived:
That is, of all the power contained in sunlight (about 1000 W/m 2) falling on an ideal solar cell, only 33.7% of that could ever be turned into electricity (337 W/m 2). The most popular solar cell material, silicon, has a less favorable band gap of 1.1 eV, resulting in a maximum efficiency of about 32%.