• A wire of radius 1.0 mm carries a current of 21.0 A. The wire is connected to a parallel plate capacitor with circular plates of radius R = 3.1 cm and a separation between the plates of s = 2.0 mm. What is the magnitude of the magnetic field due to the changing electric field at a point that is a radial distance of r = 1.0 cm from the center of the parallel plates? Neglect edge effects. (Assume the current has just begun charging the capacitor.) Ans:- 4.37*e-05 T
• Three FM radio stations covering the same geographical area broadcast at frequencies 94.9, 95.1, and 95.3 MHz, respectively. What is the maximum allowable wavelength width of the band-pass filter in a radio receiver so that the FM station 95.1 can be played free of interference from FM 94.9 or FM 95.3? Use c = 3.0 108 m/s, and calculate the wavelength to an uncertainty of 1 mm. (State your answer to two significant digits.) Ans:- 13 mm
• A voltage, V, is applied across a cylindrical conductor of radius r, length L, and resistance R. As a result, a current, i, is flowing through the conductor, which gives rise to a magnetic field, B. The conductor is placed along the y-axis, and the current is flowing in the positive y-direction. Assume that the electric field is uniform throughout the conductor. (a) Find the magnitude and the direction of the Poynting vector at the surface of the conductor. (Use the following as necessary: V, r, L, R, and μ0.) Show that = i2R
• A laser produces light that is polarized in the vertical direction. The light travels in the positive y-direction and passes through two polarizers, which have polarizing angles of 35° and 55° from the vertical, as shown in the figure. The laser beam is collimated (neither converging nor expanding), has a circular cross section with a diameter of 1.70 mm, and has an average power of 16 mW at point A. At point C, what are the magnitudes of the electric and magnetic fields, and what is the intensity of the laser light? Ans:- 1770 V/m, 5.92e-06 T, 4180 W/m^2
• A microwave operates at 565 W. Assuming that the waves emerge from a point source emitter on one side of the oven, how long does it take to melt an ice cube 2 cm on a side that is 10 cm away from the emitter if 10% of the photons are absorbed by the cube? Assume a cube density of 0.96 g/cm3. (Also assume that the ice cube is initially at 0°C but has not yet started melting, and that the ice cube maintains its shape until it absorbs enough energy to completely melt.) How many photons of wavelength 10 cm hit the ice cube per second? Ans:- 3.97 hr, 9.05e+23 photon/sec