!1!Fall 2015 PHYS1302. Exam 1. Chap19-22 Cheung. Special Code: 10 1. The force on positive charge q1 due to positive charge q2 points in the positive y direction. Which statement is true regarding the force on charge q2: (a) It points in the positive y direction with a different magnitude. (b) It points in the positive y direction with the same magnitude. (c) It points in the negative y direction with a different magnitude. (d) It points in negative y direction with the same magnitude. Answer d. 2. Due to a point charge, the magnitude of the electric field is 0.35 V/m at a distance of 0.40 m. Determine the magnitude of the charge: (a) 6.2 x10-12 C (b) 1.6 x10-11 C (c) 7.6 x10-10 C (d) 2.9 x10-9 C Answer a 3. The flux perpendicular to a closed surface is 5.0 Nm2/C. Determine the magnitude of the charge it encloses: (a). 9.1x10-12 C (b). 4.4x10-11 C (c). 3.3x1010 C (d). 5.7x1011 C Answer b 4. The electric potential at x=3m is 8 V and at x=5m is 16 V. Determine the direction and magnitude of the electric field: (a) 4 V/m, negative x direction (b) 4 V/m, positive x direction (c) 16 V/m, negative x direction (d) 16 V/m, positive x direction Answer a 5. A capacitor is charged, and the battery is disconnected. A dielectric material inserted between the plates of this capacitor will serve what role? (a) Increases the capacitance by decreasing the charge on each plate. (b) Increases the capacitance by increasing the charge on each plate. (c) Increases the capacitance by decreasing the potential difference. (d) Increases the capacitance by increasing the potential difference. Answer c 6. There is a potential difference of 12 V across a 4 Ω resistor. Determine the current: (a) 3 A (b) 4 A (c) 24 A (d) 48 A Answer a!2!7. In the figure (right) with the circuit, determine the resistance between points A and B: (a) 5.3 Ω (b) 16 Ω (c) 26 Ω (d) 37 Ω Answer a 8. A charges travels with a velocity vector parallel to the magnetic field vector. If the magnetic field is 0.5 T, the charge is 1 C, and the magnitude of the velocity if 6 m/s, determine the magnitude of the magnetic force: (a) 0.0 N (b) 3.0 N (c) 6.0 N (d)12 N answer a 9. A charged particle with $1.6 x 10-19 C moves in a magnetic field of 0.5 T with a radius of curvature of 0.3 m. Determine the particle's momentum: (a) 0.6x 10-20 kg m/s (b) 1.2x 10-20 kg m/s (c) 2.4 x 10-20 kg m/s (d) 4.8 x 10-20 kg m/s answer c 10. A magnetic field of 2.0 T is perpendicular to a current of 3.2 A flowing through a wire. Determine the force per unit length on the wire: (a) 0.0 N/m (b) 1.6 N/m (c) 5.2 N/m (d) 6.4 N/m answer d !FIGURE 1 11) The equipotential surfaces between two spherical conductors are shown in Figure 1, with the value of the potential marked for each line. What is the direction of the electric field at point F? A) towards E B) towards G!3!C) towards A D) towards D E) none of the above Answer: B FIGURE 2 12) When the switch is closed in the circuit shown in the sketch in Figure 2, the wire between the poles of the horseshoe magnet deflects upward. From this you can conclude that the left end of the magnet is A) not contributing to the wire's deflection. B) a north magnetic pole. C) a south magnetic pole. D) a magnetic monopole. E) a magnetic dipole. Answer: C !13) A long, straight wire carrying a current is placed along the y-axis. If the direction of the current is in the +y direction, what is the direction of the magnetic field due to this wire? A) clockwise, around the x-axis B) counterclockwise, around the x-axis C) counterclockwise, around the z-axis D) counterclockwise, around the y-axis E) clockwise, around the y-axis Answer: D 14) Two charges, Q1 and Q2, are separated by a certain distance R. If the magnitudes of the charges are doubled and their separation is also doubled, then what happens to the electrical force between these two!4!charges? A) It is doubled. B) It changes by a factor of 3. C) reduced by a factor of sqrt 2 . D) It is quadrupled. E) It remains the same. E 15) A proton, moving north, enters a magnetic field of a certain strength. Because of this field the proton curves downward. What is the direction of the magnetic field? A) downward B) upward C) towards the east D) towards the west E) towards the north! C