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In a wave E0 =100Vm−1. Find the poynting vector magnitude.

Solution: \(\begin{array}{l}B=\frac{E}{c}\end{array} \) \(\begin{array}{l}\left|\vec{P} \right|=\frac{EB}{\mu_{0}}\end{array} \) \(\begin{array}{l}\left|\vec{P} \right|=\frac{E^{2}}{c\mu_{0}}\end{array} \) \(\begin{array}{l}\left|\vec{P} \right|=\frac{10^{4}}{3*10^{8}*4\pi*10^{-7}} = 26.5Wm^{-2}\end{array} \)

Two weights w1 and w2 are suspended on the ends of a string on a frictionless pulley. When pulled up with an acceleration g, the tension in the string is?

Solution: \(\begin{array}{l}T1−mg=m_{1}(g+a)\end{array} \) \(\begin{array}{l}T−2mg=m_{1}a\end{array} \) for second weight \(\begin{array}{l}m_{2}g−T=m_{2}(g−a)\end{array} \) \(\begin{array}{l}2 m_{2}g−T=m_{2}a\end{array} \) \(\begin{array}{l}T =\frac{4m_{1}m_{2}g}{m_{1}+m_{2}}\end{array} \) \(\begin{array}{l}Since w1=m_{1}g and w2=m_{2}g\end{array}... View Article

A 150 m long metal wire connects points A and B. The electric potential at point B is 50V less than that at point A. If the conductivity of the metal is 60 × 10^6 mho/m then magnitude of the current density in the wire is equal to?

Solution: \(\begin{array}{l}Resistivity=\frac{1}{conductivity} = \frac{1}{60*10^{6}}\end{array} \) \(\begin{array}{l}R=\frac{\rho L}{A} \end{array} \) \(\begin{array}{l}Resistivity=\frac{1}{60*10^{6}}.\frac{150}{A}\end{array} \) \(\begin{array}{l}R=\frac{2.5*10^{-6}}{A}\end{array} \) \(\begin{array}{l}\Delta V=50V\end{array} \) \(\begin{array}{l}i=\frac{v}{r}=\frac{50}{\frac{2.5*10^{-6}}{A}}\end{array} \) \(\begin{array}{l}i=20*10^{6}A\end{array} \)... View Article

A loop is formed by two parallel conductors conducted by a solenoid with inductance L and a conducting rod of mass m, which can freely (without friction) slide over the conductors. The conductors are located in a horizontal plane in a uniform vertical magnetic field with induction B. The distance between the conductors is equal to l At the moment t=0 a constant force F starts acting on the rod. Angular frequency of motion rod is. What happens if F and m are doubled?

a) \(\begin{array}{l}\omega becomes \frac{1}{\sqrt{2}} times\end{array} \) b) \(\begin{array}{l}\omega becomes {\sqrt{2}} times\end{array} \) c) \(\begin{array}{l}\omega becomes 2 times\end{array} \) d) \(\begin{array}{l}\omega... View Article

Factors of 2700

Solution: A factor is a number that divides another number evenly (i.e with no remainder).  Factors of 2700 are 1,... View Article