HW06-solutions

# HW06-solutions - Munoz (gm7794) HW06 TSOI (92515) 1 This...

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Unformatted text preview: Munoz (gm7794) HW06 TSOI (92515) 1 This print-out should have 16 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A current is flowing clockwise around a loop placed on your desk. What would be the direction of the result- ing magnetic field inside the loop? 1. downward correct 2. no magnetic field was generated. 3. upward 4. counterclockwise 5. clockwise Explanation: By the right-hand rule, the field points down. 002 10.0 points Two long, parallel wires, fixed in space, carry currents I 1 and I 2 . The force of attraction has magnitude F . What currents will give an attractive force of magnitude 4 F ? 1. 2 I 1 and 1 2 I 2 2. I 1 and 1 4 I 2 3. 2 I 1 and 2 I 2 correct 4. 4 I 1 and 4 I 2 5. 1 2 I 1 and 1 2 I 2 Explanation: F &amp;quot; = I 1 I 2 2 a I 1 I 2 003 10.0 points Two long, parallel wires are separated by a distance 2 d , as shown below. Wire #1 carries a steady current I out of the plane of the page while wire #2 carries a steady current I into the page. d d P I I S S wire #2 wire #1 At what points in the plane of the page (besides points at infinity), is the magnetic field due to the currents zero? 1. At only point P . 2. At all points on a circle of radius d cen- tered at either wire. 3. At no points. correct 4. At all points on the line SS , a perpen- dicular bisector of a line connecting the two wires. 5. At all points on the line connecting the two wires. Explanation: The only way that the total magnetic field would be zero is if the magnetic fields due to the two wires have the same magnitude but opposite directions at the same point. Only at points on the line SS do the mag- netic fields have the same magnitude. Only at point P are the magnetic fields parallel (aligned with the vertical axis). Using the right hand rule, they are in the same direc- tions. Thus, at no points (besides points at infin- ity) is the magnetic field due to the currents zero. 004 10.0 points An electron always experiences a force in an electric field, but not always in a magnetic field. Defend this statement. Munoz (gm7794) HW06 TSOI (92515) 2 1. An electric field always acts on charged particles. The magnetic force vanishes when the velocity of the electron is parallel to the magnetic field. correct 2. If the velocity of an electron is greater than a critical value, a magnetic field cannot exert any force on the electron. 3. An electron always has a charge in an electric field, but not always in a magnetic field. 4. Away from the Earth an electron does not feel any magnetic force. 5. Sometimes a magnetic field disappears when an electron is placed in it....
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## This note was uploaded on 06/10/2011 for the course PHY 302l taught by Professor Morrison during the Summer '08 term at University of Texas at Austin.

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HW06-solutions - Munoz (gm7794) HW06 TSOI (92515) 1 This...

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