Exam 2--PHYS 202--Spring 2011

Transcription

1 ame: Exam 2--PHYS 202--Spring 2011 Multiple Choice Identify the choice that best completes the statement or answers the question 1 Which of the following equations for this circuit is correct? a -6-8I 1-3I 3-4I 1 =0 c 12-2I 2-8I 1-6-4I 1 =0 b 6-8I 1 +2I I 1 =0 d I 1 +I 3 =I 2 2 Two pieces of copper wire are the same length The diameter of wire A is twice that of wire B How do their resistances compare? a R A =R B d R A =2R B b R A =½R B e R A =4R B c R A =¼R B 3 Which lightbulb, in your house, draws more current: a 40 W or a 100 W bulb? a 40 W c both the same b 100 W 1

2 4 The following circuit is relevant for the next 4 questions What is the equivalent resistance of this circuit? a 10 Ω c 14 Ω b 70 Ω d 40 Ω 5 For the circuit in the previous figure, what is the potential across R 3? a 54 V d 30 V b 40 V e 12 V c 60 V 6 For the circuit above, if R 3 is removed from the circuit, what happens to the current through R 1? a it increases c it decreases b it remains the same 7 Consider the above circuit Which resistor has the least current travelling through it? a R 1 c R 5 b R 3 d all have the same current 2

3 8 Which of these statements about a household circuit is true: I The household circuit is a parallel circuit II All devices in a household circuit operate at the same current III As you add more devices to a household circuit, the potential across each device decreases IV The circuit breaker turns off if I in >I out for any particular device a I & II c I & IV b I d II & III 9 Which of these best describes why some materials are permanent magnets (so-called ferromagnetic )? a these materials are found in the center of c these materials are made of metal the Earth b the magnetic domains of these materials are all aligned in the same direction d these materials contain charges 10 This figure shows a loop of wire, through which current flows, in the magnetic field of a permanent magnet In which direction does the loop initially turn? a clockwise c the loop does not move b counter clockwise d there is not enough information 3

4 11 A positive charge is travelling towards a wire as shown Initially, there is no current through the wire What direction will the charge travel when the current is turned on? a down c up b into the page d out of the page 12 A negative charge enters a magnetic field as shown In what direction will it feel a force? a up d into the page b down e right c left 4

5 13 The point A is equidistance between these two, long parallel wires What is the direction of the magnetic field at point A due to the two wires? a To the right d To the left b Into the page e There is no magnetic field at A c Out of the page 14 These are types of light in the electromagnetic spectrum (listed alphabetically) Arrange them in order from lowest energy to highest energy: gamma rays microwaves radio waves ultraviolet a microwaves, ultraviolet, radio, gamma c gamma, radio, microwaves, ultraviolet b microwaves, radio, ultraviolet, gamma d radio, microwaves, ultraviolet, gamma 5

6 15 This figure shows the path that light travels through 3 different materials Which of these describes the relationship between the indices of refraction? a n 1 >n 2 <n 3 c n 1 <n 2 <n 3 b n 1 <n 2 >n 3 d n 1 >n 2 >n 3 16 In this figure, light travels from water to glass What must θ 1 be for total internal reflection to occur? (The index of refraction for water is 13; the index of refraction for glass is 15) a Total internal reflection will not occur c 42 b 60 d Select the words that best complete this sentence: The 17th century physicist Huygens proposed a theory that described light as a based on the properties observed in a wave, photoelectric effect d particle, reflection b wave, refraction e duality, diffraction c wave, interference 6

7 18 This figure shows an incoming ray that is incident on a right-angle mirror at an angle of θ 1 =30 What is the angle θ 2 for the reflected ray? (The figure is not drawn to scale) a 90 c 60 b 30 d 15 7

8 Problem 19 (25 pts) Label the currents in this circuit Calculate each current and give its magnitude and direction For extra credit (3 pts), solve the system of equations by creating the identity matrix 8

9 20 (20 pts) A particle carrying a +20 C charge moves with velocity v = 3j - 3k m/s through a uniform magnetic field B = 2i - 4j T What is the force, in vector notation, on the charged particle? 9

10 21 (15 pts) A LASER ray travels through an aquarium of water as shown in this figure What is the height from the floor (y) that the ray strikes the wall above the aquarium? (The index of refraction for water is 13) 10

11 22 (5 pts) Describe, in your own words, how an electric generator works Be brief (no more than ~25 words) 11

12 ID: A Exam 2--PHYS 202--Spring 2011 Answer Section MULTIPLE CHOICE 1 ANS: B PTS: 1 2 ANS: C PTS: 1 3 ANS: B PTS: 1 4 ANS: A PTS: 1 5 ANS: C PTS: 1 6 ANS: B PTS: 1 7 ANS: B PTS: 1 8 ANS: B PTS: 1 9 ANS: B PTS: 1 10 ANS: A PTS: 1 11 ANS: A PTS: 1 12 ANS: C PTS: 1 13 ANS: E PTS: 1 14 ANS: D PTS: 1 15 ANS: A PTS: 1 16 ANS: A PTS: 1 17 ANS: B PTS: 1 18 ANS: C PTS: 1 PROBLEM 19 ANS: PTS: 1 20 ANS: PTS: 1 21 ANS: PTS: 1 22 ANS: A coil of wire sits in a magnetic field When a force is applied to the coil, charges flow through the wire PTS: 1 1