Quest Physics Homework Magnetism 6d6i42

white (cw32974) – HW6 - Magnetism – fabi – (54328) This print-out should have 27 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001

10.0 points

An electron is in a uniform magnetic field B that is directed into the plane of the page, as shown. B

B

v

e−

B

B

When the electron is moving in the plane of the page in the direction indicated by the arrow, the force on the electron is directed

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atom, carrying a charge of 3.2 × 10−19 C moves at 5.8 × 107 m/s at a right angle to a magnetic field. If the particle experiences a force of 4.7 × 10−14 N due to the magnetic field, what is the magnitude of the magnetic field? The charge on a proton is 3.2 × 10−19 C. Answer in units of T 004 10.0 points The figure represents two long, straight, parallel wires extending in a direction perpendicular to the page. The current in the right wire runs into the page and the current in the left runs out of the page. a

b

c

What is the direction of the magnetic field created by these wires at location a, b and c? (b is midway between the wires.)

1. into the page. 1. up, down, up 2. toward the left 2. up, zero, down 3. toward the right 3. up, up, down 4. toward the bottom of the page. 4. down, down, up 5. out of the page. 5. down, up, down 6. toward the top of the page. 6. down, zero, up 002 10.0 points An electron in a vacuum is first accelerated by a voltage of 31200 V and then enters a region in which there is a uniform magnetic field of 0.607 T at right angles to the direction of the electron’s motion. The mass of the electron is 9.11 × 10−31 kg and its charge is 1.60218 × 10−19 C. What is the magnitude of the force on the electron due to the magnetic field? Answer in units of N 003 10.0 points An alpha particle (the nucleus of a helium

005 10.0 points A wire carrying a current 40 A has a length 0.1 m between the pole faces of a magnet at an angle 60 ◦ (see the figure). The magnetic field is approximately uniform at 0.5 T. We ignore the field beyond the pole pieces.

white (cw32974) – HW6 - Magnetism – fabi – (54328) I

θ

ℓ

B

010 (part 2 of 3) 10.0 points What is its kinetic energy? Answer in units of J 011 (part 3 of 3) 10.0 points What potential difference in MV would be required to give it this kinetic energy? Answer in units of MV

What is the force on the wire? Answer in units of N 006 10.0 points The two wires of length 2 m are 3 mm apart and carry a current of 10 A dc. Calculate the force between these wires. Answer in units of N 007 10.0 points A thin 2.39 m long copper rod in a uniform magnetic field has a mass of 57.9 g. When the rod carries a current of 0.269 A directed perpendicular to the magnetic field, it floats in the magnetic field. The acceleration of gravity is 9.81 m/s2 . What is the field strength of the magnetic field? Answer in units of T 008 10.0 points A small rectangular coil composed of 76 turns of wire has an area of 16 cm2 and carries a current of 1.3 A. When the plane of the coil makes an angle of 43◦ with a uniform magnetic field, the torque on the coil is 0.16 N m. What is the magnitude of the magnetic field? Answer in units of T

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012 (part 1 of 2) 10.0 points A particle of mass 1.1952 × 10−25 kg and charge of 4.8×10−19 C is accelerated from rest in the plane of the page through a potential difference of 437 V between two parallel plates as shown. The particle is injected through a hole in the right-hand plate into a region of space containing a uniform magnetic field of magnitude 0.0802 T. The particle curves in a semicircular path and strikes a detector. q m

hole

Region of Magnetic Field B

E

Which way does the magnetic field point? 1. toward the lower left corner of the page 2. toward the lower right corner of the page 3. to the left 4. toward the upper left corner of the page

009 (part 1 of 3) 10.0 points An alpha particle has a mass of 5.7 × 10−27 kg and bears a double elementary positive charge. Such a particle is observed to move through a 4.3 T magnetic field along a circular path of radius 0.18 m. The charge on a proton is 1.60218×10−19 C. What speed does it have? Answer in units of m/s

5. to the right 6. into the page 7. toward the bottom of the page 8. toward the upper right corner of the page 9. toward the top of the page

white (cw32974) – HW6 - Magnetism – fabi – (54328)

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beam will be 10. out of the page 1. deflected downward. 013 (part 2 of 2) 10.0 points What is the magnitude of the force exerted on the charged particle as it enters the region of ~ ? the magnetic field B Answer in units of N 014 (part 1 of 2) 10.0 points Consider the age of a horizontal electron beam through a velocity selector, where the ~ points downward and the magelectric field E ~ netic field B points into the paper.

B

2. deflected out of the paper. 3. deflected downward and out of the paper. 4. deflected upward and into the paper. 5. deflected upward and out of the paper. 6. deflected downward and into the paper. 7. undeflected.

v 8. deflected upward.

E 9. deflected into the paper. Based on the Lorentz force law, what is the critical speed vc (the speed at which the horizontal electron beam is not deflected)? 1. vc = B 2 E B E2 1 3. vc = BE E 4. vc = B E 5. vc = 2 B 2. vc =

016 (part 1 of 2) 10.0 points An electron in an electron beam experiences a downward force of 1.5 × 10−14 N while traveling in a magnetic field of 8.9 × 10−2 T west. The charge on a proton is 1.60×10−19 . a) What is the magnitude of the velocity? Answer in units of m/s 017 (part 2 of 2) 10.0 points b) What is its direction? 1. West 2. North

6. vc = B E B2 7. vc = E B 8. vc = E 9. vc = B E 2 10. vc =

E2 B

015 (part 2 of 2) 10.0 points If the speed of the electrons is greater than the critical speed, the trajectory of the electron

3. None of these 4. South 5. East 018 10.0 points Can an electron at rest in a magnetic field be set into motion by the magnetic field? What if it were at rest in an electric field? 1. no; yes

white (cw32974) – HW6 - Magnetism – fabi – (54328)

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2. None of these 3. It depends on the intensity of the fields, which is not provided in the problem. 4. yes; no

021 10.0 points The direction of the magnetic field in a certain region of space is determined by firing a test charge into the region with its velocity in various directions in different trials. The field direction is

5. no for both 6. yes for both 019 10.0 points A charged particle is projected with its initial velocity parallel to a uniform magnetic field. What is the resulting path? 1. circular arc. 2. spiral.

1. the direction of the velocity when the magnetic force is a maximum. 2. None of these 3. the direction of the magnetic force. 4. one of the direction of the velocity when the magnetic field is zero. 5. perpendicular to the velocity when the magnetic force is zero.

3. parabolic arc. 4. straight line parallel to the field. 5. straight line perpendicular to the field. 020 10.0 points A friend tells you that a refrigerator door, beneath its layer of white painted plastic, is made of aluminum. How could you check to see if this is true (without any scraping)?

022 10.0 points A positively charged particle es through a laboratory traveling in an easterly direction. There are both electric and magnetic field in the room and their effects on the charged particle cancel. If the electric field points upward, what must be the direction of the magnetic field? 1. upward 2. north

1. Apply a small magnet to the door. If it sticks, your friend is wrong because aluminum is not magnetic. If it doesn’t stick, your friend might be right, (but not necessarily). 2. Burn the refrigerator door and then analyze the remains with chemical reagents to find if aluminum is present. 3. Apply a small magnet to the door. If it sticks, your friend might be right because aluminum is magnetic. If it doesn’t stick, your friend might be wrong. 4. It cannot be checked without scraping the painted plastic.

3. south 4. downward 5. east 6. west 023 (part 1 of 2) 10.0 points A uniform 1.3 T magnetic field points north. If an electron moves vertically downward (toward the ground) with a speed of 4.8 × 107 m/s through this field. The charge on a proton is 1.60×10−19 . a) What is the magnitude of the force acting

white (cw32974) – HW6 - Magnetism – fabi – (54328) on it? Answer in units of N 024 (part 2 of 2) 10.0 points b) What is the direction of the force? 1. South 2. None of these 3. East 4. West 5. North 025 (part 1 of 2) 10.0 points In a nuclear research laboratory, a proton moves in a particle accelerator through a magnetic field of intensity 0.187 T at a speed of 4.25 × 107 m/s. The charge of a proton is 1.60218 × 10−19 C. If the proton is moving perpendicular to the field, what force acts on it? Answer in units of N 026 (part 2 of 2) 10.0 points If the proton of mass 1.67262 × 10−27 kg continues to move in a direction that is consistently perpendicular to the field, what is the radius of curvature of its path?. Answer in units of m 027 10.0 points A circular coil consisting of a single loop of wire has a radius of 26.1 cm and carries a current of 34.5 A. It is placed in an external magnetic field of 0.457 T. Find the magnitude of the torque on the wire when the plane of the coil makes an angle of 53.1◦ with the direction of the field. Answer in units of N · m

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