Phys 4, Section 1                      Exam 1                               Feb 16, 2001

F = kq₁q₂/r²     E = F/q     EAdA = q/ε_o         Φ = IEA dA         u = ε_oE²/2
V = W/q = -IEAds         C = Q/V         C = ε_oA/d         U = CV²/2     V = IR
P = I²R         k = 9 H 10⁹ NAm²/C²         k = 1/(4πε_o)         E = ρJ     J = I/A
R = ρL/A     I = dq/dt = nqv_dA         e^- = -1.6H10^-19 C
Series: R_eff = R₁ + R₂ + ...                       1/C_eff = 1/C₁ + 1/C₂ + ...
Parallel: 1/R_eff = 1/R₁ + 1/R₂ + ...               C_eff = C₁ + C₂ + ...

1. The equation for the force between electric charges is named after
    A) Volterra         B) Ampere         C) Gauss         D) Coulomb

2. If a neutral conducting sphere is to receive a charge opposite to that on a
    rubber rod, the sphere should be charged by
    A) conduction             B) induction             C) osmosis

3. Two small spheres of mass m = 15.0 g are hung by silk threads of length
    L = 1.20 m from a common point. When the spheres are given equal amount 
    of negative charge, each charge hangs at θ = 25.0 degrees from vertical. What
    is the magnitude of the charge q?
    A) 1.4         B) 2.8          C) 4.2         D) 5.6                               H 10^-6 C

4. Gauss=s law for electrostatics is valid
    A) for all surfaces     B) only for closed surfaces     C) only for flat surfaces

5. Electric flux has units
    A) NAm²/C         B) NAC/m²         C) NAm/C         D) CAm/s²

6. A flat sheet of paper of area 0.25 m² is oriented so that the surface of the 
    paper is oriented at 60 degrees to a uniform electric field of magnitude 
    14 N/C. What is the magnitude of the flux through the sheet?
    A) 0.82         B) 1.75          C) 2.4         D) 3.03                               NAm²/C

7. A point charge q = -6.0 nC is located on the x-axis at x = 2.00. What is the
    total electric flux due to this charge through a spherical surface centered at 
    the origin with r = 2.5 m ?
    A) 339     B) -339     C) 678     D) -678                                       NAm²/C

8. An electric dipole consists of two point charges, q₁ = +12 nC and q₂ = -12 nC
    placed 10 cm apart. What is the potential at a point 6.0 cm from the positive
    charge on the line between the two charges?
    A) -900         B) 1800          C) -1800         D)900         E) 1400             V

9. Which of the following terms is an energy term?
    A) kq₁q₂/r         B) kq₁/r         C) kq₁/r²              D) kq₁q₂/r²

10. A capacitor C is charged to a potential V. What is the total charge on the
    capacitor?
    A) CV         B) C/V          C) V/C         D) 0

11. A parallel-plate air capacitor is made by using two plates 16 cm square, spaced
    4.7 mm apart. It is connected to a 12 V battery. What is the charge on the
    positive plate?
    A) 0.12         B) 0.24          C) 0.58         D) 0.64         E) 0.82                 nC

12. A copper wire has a diameter of 1.02 mm and carries a current of 1.67 A. If the
    density of free electrons in the wire is 8.5 H 10²⁸ per cubic meter, what is the
    drift velocity of the electrons?
    A) 0.05         B) 0.10          C) 0.15         D) 0.20         E) 0.25           mm/s

13. What is the resistance of a 100 watt light bulb designed for a 100 volt supply?
    A) 50         B) 100          C) 150         D) 200         E) 250                    Ω

14. A battery-powered GPS receiver operating on 9.0 V draws a current of 0.13 A.
    How much energy does it use in 1.5 hours?
    A) 1.2         B) 2.6          C) 3.4         D) 5.1         E) 6.3                     KJ

15. Two capacitors of different capacitance values are to be used to achieve the
    maximum possible effective capacitance. How should they be joined?
    A) series         B) parallel             C) just use the larger one

16. A three-ohm and a six-ohm resistor are joined in parallel; then a four-ohm and
    a twelve-ohm resistor are joined in parallel. Finally the two sets are joined in
    series and a 60 volt battery is placed across the entire combination. How much
    power is drawn from the battery?
    A) 120         B) 240          C) 360         D) 560         E) 720                   W

Last modified on February 13, 2002