Pressure = Force/Area. Force = mass × acceleration, dimensions [MLT⁻²]. Area = L². So pressure = [MLT⁻²]/[L²] = [ML⁻¹T⁻²]. This is also the dimension of stress. Common exam trap: confuse with energy density which is also [ML⁻¹T⁻²].
Explanation:
Fuse wire must melt easily (low melting point) to break circuit on overload, and have high resistance to produce sufficient heat (I²R). Materials: tin-lead alloy. Copper not used as fuse.
Explanation:
Laser (Light Amplification by Stimulated Emission of Radiation) requires that more atoms exist in a high-energy excited state than in a lower energy state. This unnatural, non-equilibrium condition is called 'population inversion'. Without it, absorption would dominate over stimulated emission, and the beam would not be amplified.
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