Question

# 1) 2 point charges are separated by a distance of 8 cm. The left charge is...

1) 2 point charges are separated by a distance of 8 cm. The left charge is 48 mC and the right charge is -16mC. Using a full sheet of paper: draw the 2 charges separated by 8cm, centered in the sheet. (if you are missing a ruler estimate 8cm as ⅓ a paper sheet length). [6] a) Draw field lines to indicate the electric fields for this distribution. [4] b) Draw 3 equipotential surfaces, 1 each, that pass: -Through the center position between the charges. -Through the point 4cm left of the left charge -Through the point 4cm right of the right charge _______________________________________________________________________ 2) In the charge distribution described above in Question #1, a test charge of 1C is positioned at the center of these 2 charges. [10] Determine the force on the test charge. _______________________________________________________________________ 3) A large battery is charged to a potential of 12.5 Volts. The addition of more charge changes the voltage by a negligible amount, a characteristic of the “ideal battery”. A 5amp charger is connected for 48 minutes to increase the stored energy.. [2] a) Determine the amount of charge that is moved. [2] b) Determine the effective resistance of the charging circuit. [3] c) Determine how much work is done during this time? [3] d) Determine the drift speed of the charges in the charging wires, 2mm in diameter of copper with a molar density of 0.14 mol/cc. _______________________________________________________________________ 4) A multi-layer capacitor is made from a stack of 6 metal plates separated by thin layers of plastic. The plastic is 0.2mm thick. The copper plates are 1mm thick. Each component is a square with 10cm sides. Plastic has a relative dielectric constant of 2.4 and copper has a resistivity of 1.7e-8 ohm-meters and this capacitor is charged to a 1V potential.. [6] a) Determine the effective capacitance of this capacitor. [4] b) Determine the electric field at the center of this multilayer capacitor in the middle of the center plastic sheet. ______________________________________________________________________ 5) A 1 microF capacitor is charged through a 2Mohm resistor using a 1.5V power source starting at t=0 with no charge. [2] a) Determine the time constant. [4] b) How many time constants will it take to reach 1.48 Volts. [2] c) How much energy is stored in the fully charged capacitor? [2] d) 1/2 microF capacitors and 1/2 Mohm resistors are available. Draw an equivalent circuit using these components. ______________________________________________________________________ 3 of 4 6) At sunset, sunlight is scattered by the atmosphere. A person looking straight up with the sun in their back sees this as the blue sky. [3] a) Explain in 50 words and/or a figure what the orientation of the electric and magnetic fields are that enter the eye. [3] b) Explain in 50 words and/or a figure why the scattered light must have only this polarization. [4] c) The Poynting vector here is 2 W/m2 . What is the amplitude of the magnetic field? ________________________________________________________________________ 7) A vertically polarized, laser beam with a wavelength of 470nm travels west. The laser beam has a diameter of 2mm. [3] a) What is the energy, in electron Volts (eV), of these photons? [3] b) What is the colour, oscillation frequency and speed of the photon [4] c) This beam is incident normal to the surface of a 1mg mylar mirror in free fall in vacuum. Determine the required laser power for a force magnitude equivalent to gravity. ___________________________________________________________________________ 8) Sunlight with an angle of incident of 30 degrees hits a thin oil layer, floating on a puddle of water. The oil layer is 185nm thick and has an index of refraction of 1.49, the water has an index of 1.33 and is 2mm thick. [6] a) There is a dominant reflection of this light at what wavelength? [2] b) What colour would this reflection appear? [2] c) Describe in 20 words or less the polarization of the reflected light: use at least 3 from the list here to describe the polarization of this reflection: ------polarized, linear, vertical, horizontal, right-handed, left-handed, elliptical, circular, unpolarized, partially polarized------ _________________________________________________________________________ 9) [3] a) A soap film appears invisible when it approaches a zero-thickness. In 50 words and/or a figure, explain why. [1] b) The north pole attracts the south pole of a compass needle allowing navigation. T/F [1] c) There are 3 colour sensors in the eye with maximum responsivity centered on the primary colours red, yellow and blue. T/F [1] d) A “red/green colour blind” person is able to detect only red or green light, not the other. T/F [2] e) Unpolarized white light is incident on a glass plate at Brewster’s angle. Some of the light is reflected, some is transmitted. Describe the polarization and colour of the reflected beam using 50 words and/or a figure. [2] f) Describe the polarization and colour of the transmitted beam using 50 words and/or a figure. __________________________________________________________________________ 4 of 4 10) A vertically polarized radio wave is detected using a circular loop of wire connected to an amplifier to detect the magnetic field. The loop has a radius of 20cm. The signal travels north and has an intensity of 0.1 W/m2 and a wavelength of 1.5 meters. [2] a) For the optimal reception, the loop should be oriented in what way? <20 words [4] b) Determine the magnetic field of this EM wave. [4] c) Determine the maximum emf generated across this antenna.. __________________________________________________________________________ 11) [5] a) A 0.005C point charge is enclosed in a spherical shell. The charge is at the center. Determine the electric flux through a 45 degree half-angle cone, at the top of the shell. [5] b) Radio waves with a frequency of 105.5MHz pass through a 2.1m tall, open door in a very large metal building. The door is 0.8 meters wide. A radio receiver 7 meters inside the door picks up the signal well when positioned directly in front of the door, in view of the CN tower from which it is broadcast. As the radio is moved to the left or right the signal dies to a minimum. How far is it moved to achieve this minimum? ________________________________________

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