# Physics: Magnetic Field and Direction

Topics: Magnetic field, Magnetism, Magnetic moment Pages: 12 (2596 words) Published: April 4, 2013
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University Physics with Modern Physics, 13e Young/Freedman

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H9 Chapter 28: Sources of Magnetic field, Ampere's law, Magnetic materials Overview Summary View Diagnostics View Print View with Answers

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H9 Chapter 28: Sources of Magnetic field, Ampere's law, Magnetic materials Due: 11:59pm on Monday, November 12, 2012 Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy

Exercise 28.2
In the Bohr model of the hydrogen atom, the electron moves in a circular orbit of radius with a speed of .

Part A
If we are viewing the atom in such a way that the electron's orbit is in the plane of the paper with the electron moving clockwise, find the magnitude of the electric field that the electron produces at the location of the nucleus (treated as a point). Express your answer using two significant figures. ANSWER: = 5.1×1011

Part B
Find the direction of the electric field that the electron produces at the location of the nucleus (treated as a point). ANSWER: from the electron toward the electron out of the page into the page

Part C
Find the magnitude of the magnetic field that the electron produces at the location of the nucleus (treated as a point). Express your answer using two significant figures. ANSWER: = 13

Part D
Find the direction of the magnetic field that the electron produces at the location of the nucleus (treated as a point). ANSWER:

from the electron toward the electron out of the page into the page

Exercise 28.16
A square wire loop 11.0 on each side carries a clockwise current of 15.0 .

Part A
Find the magnitude of the magnetic field at its center due to the four 1.20 ANSWER: = = 2.38×10−6 wire segments at the midpoint of each side.

Part B
Find the direction of this magnetic field. ANSWER: into the page out of the page

Direction of the Magnetic Field due to a Wire Conceptual Question Find the direction of the magnetic field at each of the indicated points. For the following two questions consider the wire shown in the figure. .

Part A
What is the direction of the magnetic field at Point A?

Hint 1. The magnitude of the magnetic field due to a long, straight, current-carrying wire The magnitude of the field is directly proportional to the current flowing in the wire and inversely proportional to the distance

from the wire: .

Hint 2. The direction of the magnetic field due to a long, straight, current-carrying wire The magnetic field surrounding a long, straight wire encircles the wire, as shown in the figure:

The direction of the field is determined by a right-hand rule: Grasp the wire with the thumb of your right hand in the direction of the current flow. The direction in which your fingers encircle the wire is the direction in which the magnetic field encircles the wire.

ANSWER: is out of the page. is into the page. is neither out of nor into the page and . .

Part B
What is the direction of the magnetic field ANSWER: is out of the page. is into the page. is neither out of nor into the page and . . at Point B?

Part C
What is the direction of the magnetic field at Point C?

Hint 1. How to approach the problem

To determine the direction of the magnetic field at Point C, you must determine the contribution to the field from both of the wires. The field at Point C is the vector sum of these two contributions. Keep in mind that if the magnetic fields are in opposite directions, the larger field will decide the direction of the net magnetic field. If they are the same size, the net magnetic field will be zero.

Hint 2. Find the direction of the magnetic field at Point C due to wire 1 Is the magnetic field from wire 1 directed out of or into the screen...