
21 An incandescent light bulb is supplied with a constant potential difference of
120 volts. As the filament of the bulb heats up, its resistance
(1) increases and the current through it decreases
(2) increases and the current through it increases
(3) decreases and the current through it decreases
(4) decreases and the current through it increases


22 During a thunderstorm, a lightning strike transfers 12 coulombs of charge in
2.0 × 10^{–3} second. What is the average current produced
in this strike?
(1) 1.7 × 10^{–4} A
(2) 2.4 × 10^{–2 }A
(3) 6.0 × 10^{3} A
(4) 9.6 × 10^{3} A


Note that question 23 has only three choices.
23 A 30.ohm resistor and a 60.ohm resistor are connected in an electric
circuit as shown below. Compared to the electric current through the 30.ohm
resistor, the electric current through the 60.ohm resistor is
(1) smaller
(2) larger
(3) the same


24 An operating electric heater draws a current of 10. amperes and has a
resistance of 12 ohms. How much energy does the heater use in 60. seconds?
(1) 120 J
(2) 1200 J
(3) 7200 J
(4) 72,000 J


25 If the charge on each of two small charged metal spheres is doubled and the distance
between the spheres remains fixed, the magnitude of the electric force between the
spheres will be
(1) the same
(2) two times as great
(3) onehalf as great
(4) four times as great


26 The diagram below represents a periodic wave. Which two points on the wave are
in phase?
(1) A and C
(2) B and D
(3) A and D
(4) B and E


27 A beam of monochromatic light travels through flint glass, crown glass, Lucite,
and water. The speed of the light beam is slowest in
(1) flint glass
(2) crown glass
(3) Lucite
(4) water


28 A standing wave pattern is produced when a guitar string is plucked. Which characteristic
of the standing wave immediately begins to decrease?
(1) speed
(2) wavelength
(3) frequency
(4) amplitude


29 A source of sound waves approaches a stationary observer through a uniform medium.
Compared to the frequency and wavelength of the emitted sound, the observer would
detect waves with a
(1) higher frequency and shorter wavelength
(2) higher frequency and longer wavelength
(3) lower frequency and shorter wavelength
(4) lower frequency and longer wavelength


30 What is the smallest electric charge that can be put on an object?
(1) 9.11 × 10^{–31} C
(2) 1.60 × 10^{–19} C
(3) 9.00 × 10^{9} C
(4) 6.25 × 10^{18} C


31 Which characteristic of electromagnetic radiation is directly proportional to
the energy of a photon?
(1) wavelength
(2) period
(3) frequency
(4) path


32 What is the maximum height to which a 1200watt motor could lift an object weighing
200. newtons in 4.0 seconds?
(1) 0.67 m
(2) 1.5 m
(3) 6.0 m
(4) 24 m


33 A spring of negligible mass has a spring constant of 50. newtons per meter.
If the spring is stretched 0.40 meter from its equilibrium position, how
much potential energy is stored in the spring?
(1) 20. J
(2) 10. J
(3) 8.0 J
(4) 4.0 J


34 How much current flows through a 12ohm flashlight bulb operating at 3.0
volts?
(1) 0.25 A
(2) 0.75 A
(3) 3.0 A
(4) 4.0 A


35 Which diagram below best represents the phenomenon of diffraction?


36 The displacementtime graph below represents the motion of a cart initially moving
forward along a straight line. During which interval is the cart moving forward
at constant speed?
(1) AB
(2) BC
(3) CD
(4) DE 

37 The diagram below represents shallow water waves of wavelength λ passing
through two small openings, A and B, in a barrier. How much longer is the length
of path AP than the length of path BP?
(1) 1λ
(2) 2λ
(3) 3λ
(4) 4λ


Note that question 38 has only three choices.
38 In the diagram below, lamps L_{1} and L_{2} are connected to
a constant voltage power supply. If lamp L_{1} burns out, the brightness
of L_{2} will
(1) decrease
(2) increase
(3) remain the same


39 What is the approximate mass of a pencil?
(1) 5.0 × 10^{–3} kg
(2) 5.0 × 10^{–1} kg
(3) 5.0 × 10^{0} kg
(4) 5.0 × 10^{1} kg


40 What is the minimum energy needed to ionize a hydrogen atom in the n = 2 energy
state?
(1) 13.6 eV
(2) 10.2 eV
(3) 3.40 eV
(4) 1.89 eV
