EE 1301 Exam 3 December 4, 2017 NAME Student ID 9. The antenna pattern is for wh
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EE 1301 Exam 3 December 4, 2017 NAME Student ID 9. The antenna pattern is for which antenna type (a) Isotropic Antenna (b) Directional Antenna (c) Omni-antenna (d) A &C; 10. Harry Nyquist discovered he relationship between sampling rate and the that comprise a complex signal. This relationship states that the frequencies maximum sampling rate is (a) 2X the highest frequency (b) The lower of 2X the lowest in a complex signal. frequency or 2X the highest frequency in a complex signal. (c) Twice the highest frequency in the complex signal. (d) None of these. 11. In order make a digital recording of a voice signal with tones at 240 Hz, 720 Hz. and 2400 Hz, you should use a sampling frequency of (a) 2600 samples per second (b) 5200 samples per second (c) 8000 samples per second (d) 44,100 samples per second 12. (5 pts.) A description of the operation of a DC motor would include the following concepts: (a) Magnets attract or repel (b) Batteries provide current (c) Faraday's Law (d) Oersted's Law (e) A, B, D to create an electromagnet 13. If the battery connected to a brushed DC motor is reversed, what changes direction of motion? (a) The armature (b) The commutator (c) The stator (d) A and CExplanation / Answer
9]Isotropic Pattern - an antenna pattern defined by uniform radiation in all directions, produced by an isotropic radiator (point source, a non-physical antenna which is the only nondirectional antenna). Directional Pattern - a pattern characterized by more efficient radiation in one direction than another (all physically realizable antennas are directional antennas). Omnidirectional Pattern - a pattern which is uniform in a given plane.Therefore its a Directional Antenna.
10] Nyquist Theorem says that , in order to reproduce a signal from its discretised version MINIMUM Sampling frequency should be equal totwice the highest message frequency. Option a) and c) are same.
11] Highest message frequency is 2400 Hz. Therefore Sampling Frequency should be greater than 2 x 2400 Hz. therefore choose 5200 Hz as it is closest to 4800 Hz.
12] Ina DC motor, rotor that is armature rotates. The armature contains electromagnet which crates magnetic field around it when current is passed through it. This electomagnet attracts or repel the permanent magnets in stator and thus rotor rotates. Oerested law states that electric current produces magnetic field. So options a, b and d are correct.
13] As stated in question 12, ans is a. Because current gets reversed in rotor after reversing polarity of battery. (Rotor is armature.)
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