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Energy of a photon having wave number 1.00 cm^{-1} is

a) \(\begin{array}{l}6.62*10^{-32}J\end{array} \) b) \(\begin{array}{l}1.99*10^{-23}J\end{array} \) c) \(\begin{array}{l}6.62*10^{-34}J\end{array} \) d) \(\begin{array}{l}1.99*10^{-36}J\end{array} \) Solution: b) \(\begin{array}{l}1.99*10^{-23}J\end{array} \) Explanation: \(\begin{array}{l}E=ht=h_{c}\end{array} \) \(\begin{array}{l}h=6.62*10^{-34\lambda}Js\end{array}... View Article

Time constant of the given circuit is τ. If the battery is replaced by an AC source having voltage V=V0 cosωt, the power factor of the circuit will be?

Solution: Explanation: \(\begin{array}{l}cos\phi = \frac{R}{Z}\end{array} \) \(\begin{array}{l}\tau = \frac{L}{R}\end{array} \) \(\begin{array}{l}Z=\sqrt{R^{3}+X_{L}^{2}}\end{array} \) \(\begin{array}{l}X_{L}=\omega L\end{array} \) \(\begin{array}{l}cos\phi = \frac{R}{\sqrt{R}^{2}+\omega^{2}L^{2}}\end{array} \) \(\begin{array}{l}cos\phi... View Article

Two coils have self-inductance L1=4mH and L2=1mH respectively. The currents in the two coils are increased at the same rate. At a certain instant of time both coils are given the same power. If i1 and i2 are the currents in the two coils, at that instant of time respectively, then the value of (i1 /i2) is :

a) 0 b) 1 c) ½ d) ¼ Solution: d) ¼ Explanation: \(\begin{array}{l}i_{1}V_{1}=i_{2}V_{2}\end{array} \) \(\begin{array}{l}i_{1}L_{1}\frac{di_{1}}{dt}=L_{2}\frac{di_{2}}{dt}i_{2}\end{array} \) \(\begin{array}{l}i_{1}4*\frac{di_{1}}{dt}=1\frac{di_{2}}{dt}i_{2}\end{array} \) \(\begin{array}{l}Therefore, 4i_{1}=i_{2}\end{array}... View Article