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La materia se compone de pequeñas
partículas llamadas átomos. ¿Cuál de los
siguientes científicos estableció que los
electrones giran alrededor de un núcleo en
varios niveles de energía?

A Joseph John Thomson
B Ernest Rutherford
C John Dalton
D Niels Bohr

The correct answer is D) Niels Bohr​

Explanation:

Bohr proposed a new atomic model, whereby he explains that electrons rotate around the nucleus at well-defined levels, describing circular orbits. Each orbit was called the energy level (it is called the main quantum number n, going from numbers 1 to 7). To make his model, Bohr studied the Hydrogen atom (it has a proton in its nucleus and an electron rotating around it).

dynamic equilibrium is the answer.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.