exam2Solution05

exam2Solution05 - Alpha particles (charge = +2e, mass =...

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1. Alpha particles (charge = +2e, mass = 6.68 x 10 -27 kg) are accelerated in a cyclotron to a final orbit radius of 0.90 m. The magnetic field in the cyclotron is 0.20 T. The period of circular motion of the alpha particles is closest to: *a. 0.65 µ s b. 1.0 µ s c. 1.3 µ s d. 1.6 µ s e. 2.0 µ s General Feedback: The radius is given by mv R qB = The period can be found from the tangential speed and the circumfernce 2 r v T π = Substituting 7 2 2 6.5 10 mR R qBT m Ts qB = == × 2. If you were to cut a small permanent bar magnet in half, a. one piece would be a magnetic north pole and the other piece would be a south pole. b. neither piece would be magnetic. *c. each piece would in itself be a smaller bar magnet with both north and south poles. d. each piece would contain both north and south poles, but on a given piece the intensity of the north and south poles would not necessarily be equal. e. None of these statements is true. 3. Which of the following is an accurate statement? a. Magnetic field lines have as their sources north and south poles. b. A magnetic field line is, by definition, tangent to the direction of the magnetic force on a moving charge at a given point in space. *c. The magnetic force on a moving charge does not change its energy. d. The magnetic force on a current carrying wire is greatest when the wire is parallel to the magnetic field. e. A current carrying loop of wire tends to line up with the plane of loop parallel to an external magnetic field in which it is positioned.
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4. In the above figure, a wire segment 1.2 m long carries a current I = 3.5 A, and is oriented. A uniform magnetic field of magnitude 0.50 T is present as shown. Right-handed coordinates are used. The magnetic force on the wire segment, Newtons, is closest to: a. +2.1 ˆ k b. -1.3 ˆ k c. +1.3 ˆ k d. - 1.6 ˆ k *e. + 1.6 ˆ k General Feedback: Redrawing the vectors shows that the force is into the page, i.e. parallel to the z-axis The magnitude of the force is sin(130) 1.6 Fi L B N ==
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5. A rigid circular loop has a radius of 0.20 m and is in the x-y plane. A clockwise current I is carried by the loop, as shown. A uniform external magnetic field, B = 0.20 T in the positive x-direction, is present. In the above figure, the loop is released from rest. The initial motion of the loop is described by: a. points a, b, c, and d move clockwise b. points a, b, c, and d, move counterclockwise *c. point a moves out of the plane; point c moves into the plane d. point b moves out of the plane; point d moves into the plane e. point c moves out of the plane; point a moves into the plane General Feedback: The force at point a is out of the page, the force at point c is into the page 6. A point charge Q moves on the x-axis in the positive direction with a speed of 440 m/s. A field point is on the y-axis at y = + 50 mm. The magnetic field produced at the field point, as the charge moves through the origin, is .
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exam2Solution05 - Alpha particles (charge = +2e, mass =...

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