Unformatted text preview: PHY2054 TEST II MULTIPLE CHOICE . Choose the one alternative that best completes the statement or answers the question. 1) The resistivity of gold is 2.44 x 10'8 Q - m at a temperature of 20°C. A gold wire, 1.8 mm in diameter and 14 cm
long, carries a current of 480 ma. The power dissipated in the wire is closest to:
A) 0.077 mW B) 0.25 mW C) 014 mW D) 0.19 mW @31 mW 2) A 6.0 V battery that can store 500.0] of energy is connected to a resistor. How much electrical charge must ﬂow between the battery's terminals to completely drain the batte ‘ it is fully charged?
A) 0.01 C B) 0.07 C C D) 3000 C 3) An electron enters a magnetic field of 0.69 T with a velocity perpendicular to the direction of the field. At what
frequency does the electron traverse a circular path? (The mass of an electron is 9.1 x 10-31 kg, and the charge of
an electron is 1.6 x 10-19 C.) ' A) 1.9 x 1014 Hz B) 5.3 x 10-7 Hz @9 x 1010 Hz D) 5.3 x 10-11 Hz a circular coil of wire of 200 turns and diameter 6 an carries a current of 7 A. It is placed in a magnetic field of
I. with the plane of the coil making an angle of 30° with the magnetic ﬁeld. What is the torque on the coil?
A) 1Norn B)1.8N-m C)8.2N-m D)1.5Nom E)5.9Nom 5) A negatively charged particle is moving to the right, directly above a wire having a current ﬂowing to the right,
as shown in Figure 1. In which direction is the magnetic force exerted on the particle? Figure 1
A) into the page B) out of the page pward D)downward E)the magnetic force is zero.
6) Figure 2
59 uF 6.8 MG Initially, for the circuit shown, the switdt Sis open and the capacitor voltage is 80 V. The switch S is closed at
time t = 0. In Figure 2, the capacitor voltage when the time t is equal to 40.0 s is closest to:
A)91V B)110V C)81V D) 100V @ZV 7) A very long straight current-carrying wire produces a magnetic ﬁeld of 20 mT at a distance d from the wire. To
measure a ﬁeld of 5 mT due to this wire, you would have to go to a distance of A) Mi B) 811 C) 16d D) 2d 8) A charged particle of mass 0.0040 kg is subjected to a 4.0 T magnetic ﬁeld which acts at a right angle to its
motion. If the particle moves in a circle of radius 0.10 m at a speed of 2.0 m/s, what is the magnitude of the charge on the particle?
A) 000040 c .020 c C) 50 c D) 2500 c 9) A square wire 2.0 cm on each side is oriented so that a 5.00 mT magnetic ﬁeld makes a 30.0° angle with the
normal to the plane of the square. If a 1.0 mA current causes a 32.0 N - m torque on the wire, how many loops
does the wire make? ' A) 4.5 x 1010 B) 3.2 x 106 C) 1.6 x 1010 .2 x 1010 10) A charged particle moving within a static magnetic field
A will always experience a magnetic force, regardless of its direction of motion.
éay experience a magnetic force, but its speed will not change.
may experience a magnetic force which will cause its speed to change.
D) None of the above statements are true. Regular Problem (10 points each). 11. In Figure 3, the two long straight wires are separated by a distance of d = 0.40 m. The currents are 11 = 1.0 A to the right in
the upper wire and 12 = 8.0 A to the left in the lower wire. Find the magnitude and direction of the magnetic field at th( center point 0, and also point P, a distance d/2 = 0.20 m below the lower wire? (NOTE: p0 = 411 x 10'7T - m/A.)
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