The First Law of Thermodynamics is essentially a specific application of which fundamental principle of physics?
A. Conservation of Momentum
B. Newton's Third Law
C. Conservation of Energy
D. Conservation of Mass
Answer: Option C
Solution (By JKSSB Mock Tests)
The first law of thermodynamics states that the heat supplied to a system (dQ) is equal to the change in its internal energy (dU) plus the work done by the system (dW): dQ = dU + dW. This is the law of conservation of energy applied to thermodynamic systems, stating that energy cannot be created or destroyed, only transferred or changed in form.
In a photoelectric effect experiment, a graph is plotted between the stopping potential (V0) on the y-axis and the frequency of incident light (v) on the x-axis. The slope of this straight line gives the value of:
A.Planck's constant (h)
B.Work function of the metal
C.Planck's constant divided by electron charge (h/e)
Explanation:
Einstein's photoelectric equation is K_max = hv - W. Since K_max = eV0 (where V0 is stopping potential), eV0 = hv - W. Rearranging for the y-axis variable gives V0 = (h/e)v - (W/e). This is a linear equation y = mx + c. The slope 'm' of the V0 vs v graph is strictly exactly h/e.
Explanation:
Henri Becquerel discovered natural radioactivity in 1896 from uranium salts. Marie and Pierre Curie later discovered radium and polonium. Rutherford classified alpha, beta rays. Roentgen discovered X-rays.
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