1 19 2ndTriExam March 2016

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JMJ

Student’s Name _______________________ Physics H Second Trimester Examination March 21, 2016 8:40 am Bro. Nigel, Mr. Ditrano, Mr. Mauser and Mr. Sorkin PART I. Multiple choice questions. Choose the best answer for each question and fill-in the appropriate oval on the scantron sheet provided. (0.5 points each) 1. Which part of an atom is most likely to be transferred as an electrostatic charge increases on an object? (a) positrons (b) neutrons (c) protons (d) electrons 2. When a rod is brought near a neutral electroscope, the leaves diverge. Which statement best describes the charge on the rod?

(a) It must be positive (b) It must be negative (c) it must be neutral (d) It can be either a positive or a negative charge

3. A glass rod is given a positive charge by rubbing it with silk. The most likely reason for the charge on the rod is because it has

(a) gained electrons (b) lost electrons (c) gained protons (d) lost protons

4. Which procedure doubles the force between two charges?

(a) halving the magnitude of one of the charges (b) doubling the magnitude of one charge (c) doubling the distance between the charges (d) halving the distance between the charges

5. Which of the following could be most closely associated with charging by induction?

(a) touching both end of an outlet at the same time (b) the experience you may have if you place your tongue on both terminal of a 9 V battery (c) sitting in a car that has a live wire on the top (d) the build up and discharge of lightning

6. Compared to the force of the electric field of sphere X on sphere Y, the force of the electric field of sphere Y on sphere X is

(a) less (b) greater (c) the same

7. If the diameter of a wire were to increase, its electrical resistance would

(a) increase (b) decrease (c) remain the same

8. If the potential difference across a wire conductor increases, the current in that wire will

9. If the resistance in a conductor increases, the current through that conductor will

(a) increase (b) decrease (c) remain the same 10. If the voltage across a 12-ohm resistor is 4.0 volts, the current through the resistor is

(a) 4.0 A (b) 3.0 A (c) 48 A (d) 0.3 A 11. As the temperature of a metallic conductor increases, its resistance usually

(a) increases (b) decreases (c) remains the same 12. If the length of a conducting wire is increased, the resistance to the flow of current will

13. Potential difference across a conductor is known as (a) the voltage (b) the resistance (c) the current (d) joules

14. A 10-volt potential difference maintains a 2- ampere current in a resistor. The power expended by the resistor is

(a) 5 watts (b) 10 watts (c) 20 watts (d) 40 watts 15. Three resistances of 2 ohms, 4 ohms and 6 ohms are connected in parallel. The equivalent resistance of the three resistors is

(a) greater than 6 ohms (b) less than 2 ohms (c) between 4 ohms and 6 ohms (d) between 2 and 4 ohms

16. An electric heater rated at 4800 watts is operated on 120 volts. What is the resistance of the heater?

(a) 3.0 ohms (b) 576 000 ohms (c) 120 ohms (d) 40 ohms

17. As the number of turns in the secondary coil of a transformer decreases, the voltage in the primary coil will

18. Two electric light bulbs are connected in parallel. A third light bulb is added on another parallel branch. The total current in the 3 branches will

19. A magnetic field is produced by

(a) stationary ions (b) moving electrons (c) aligned domains (d) stationary electrons

20. The physical structure of an electric motor most closely resembles that of

(a) a transformer (b) cathode (c) diode (d) generator 21. A difference between electrical forces and gravitational forces is that electrical forces include (a) separation distance (b) repulsive interactions (c) the inverse square law (d) all of these

22. In a good insulator, electrons are usually (a) free to move around (b) free to move after an impurity has been added (c) semi-free to move around (d) tightly bound in place

23. To be safe in the unlikely case of a lightning strike, it is best to be inside a building framed with

(a) steel (b) wood (c) either of these

24. Much electronic equipment contains transistors that are in turn made from semiconductors. Semiconductors (a) can conduct electricity (b) can be very good insulators (c) contain helpful impurities (d) all of these 25. Coulomb’s law says that the force between any two charges depends ____________.

(a) directly on the size of the charges (b) inversely on the square of the distance between the charges (c) both a and b (d) none of these

26. An electroscope is charged positively, as shown by the foil leaves that stand apart. As a negative charge is touched to the electroscope, the leaves

(a) move closer together (b) spread father apart (c) do not move

27. Which of the folloing methods of charging involve no contact?

(a) induction (b) friction (c) contact (d) deduction 28. Bring a charged object near a conductor and then momentarily touch it to a conductor. This demonstrates charging by

(a) induction (b) friction (c) polarization (d) contact

29. The reason a charged balloon will stick to a wall is (a) the charge is slightly sticky and acts like glue (b) electrons transfer back and forth between the wall and the balloon (c) induced opposite charges in the wall are closer than other wall charges (d) balloon material simply sticks to the wall

30. Two charged particles held close to each other are released. As they move towards each other, the force on each particle increases. Therefore, the particles have (a) the same sign (b) opposite signs (c) none of these 31. The end of one magnet and the opposite end of another magnet held near each other are released, the force on each magnet

(a) increases (b) decreases (c) remains the same 32. If you walk into a region of space and suddenly feel a force, the space is said to contain a

(a) black hole (b) charged object (c) force field (d) heavy object

33. An electric field has

(a) magnitude (b) direction (c) both of these

34. The electric field outside a Van de Graaf generator may be enormous, while inside the spherical dome, the electric field is

(a) zero (b) the same (c) twice as much (d) ½ as much 35. In order for a continuous flow of charge from one place to another, there must be

(a) potential difference between the two places (b) conductor connecting the two places (c) both of these (d) none of these

36. The primary reason that a bird can perch harmlessly on a bare high voltage wire is that

(a) a bird has a very high electric potential (b) the bird’s feet are close together (c) there is no potential difference across the bird’s feet (d) all of these

37. Alternating current is made by

(a) alternating the direction of the voltage of the power source (b) huge chemical batteries (c) inverting the potential (d) alternating both current and voltage 38. Current from a battery is always

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39. Power outlets in our home typically have a potential difference of

(a) 240 V (b) 120 A (c) 120 V (d) 60 A

40. When a 10 V battery is connected to a resistor, 2 A of current flows in the resistor. What is the resistor’s value?

(a) 2 ohms (b) 5 ohms (c) 10 ohms (d) 20 ohms 41. The current through a 10-ohm resistor connected to 120 V is

(a) 1 A (b) 10 A (c) 12 A (d) 120 A

42. A 10-ohm resistor has a 5 A current in it. What is the voltage across the resistor?

(a) 50 V (b) 10 V (c) 15 V (d) 20 V

43. What is the resistance of a toaster that uses 2 A of current when connected to a 120 v power source? (a) 20 ohms (b) 120 ohms (c) 60 ohms (d) 2 ohms 44. How much power is used by a 6 V battery that draws 0.5 A of current?

(a) 30 W (b) 12 W (c) 6 W (d) 3 W

45. A 60-watt light bulb is connected to 120 V. How much current exists in the light bulb?

(a) 0.25 A (b) 0.5 A (c) 2 A (d) 4 A 46. Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have

(a) more resistance (b) less resistance (c) the same resistance

47. The total resistance of a 3-ohm resistor and a 6-ohm resistor in series is

(a) 18 ohms (b) 9 ohms (c) 6 ohms (d) 3 ohms (e) 2 ohms

48. The total resistance for the same two resistors connected in parallel is

(a) 18 ohms (b) 9 ohms (c) 6 ohms (d) 2 ohms 49. As the number of aligned magnetic domains increases in a bar of iron, the strength of the magnetic field around the bar will

(a) increase (b) decrease (c) remain the same 50. Moving electric charges will interact with

(a) an electric field (b) a magnetic field (c) both of these (d) none of these

51. As the number of loops in a coil of wire increases, the magnetic filed strength around the wire will (a) increase (b) decrease (c) remain the same 52. If you break a bar magnet in half, each half (a) contains one magnetic pole (b) becomes a bar magnetic with two poles (c) becomes unmagnetized 53. Which of the following materials is magnetic? (a) iron (b) nickel (c) cobalt (d) all of these 54. The Earth’s magnetic field is most likely due to (a) millions of small magnets buried in the earth (b) convection currents in the molten part of the earth’s interior (c) the rotation of the earth acting on all of the electrons in the earth (d) a magnetized solid inner core of the earth

55. Electric current can best be induced in a wire by (a) moving the wire up and down (b) setting the wire near a magnet (c) moving a magnet up and down near the wire (d) rotating the wire

56. A magnet is moved in and out of a coil of wire connected to a high resistance voltmeter. If the number of coils doubles, the induced voltage

(a) quadruples (b) doubles (c) remains the same (d) halves

57. A device that converts mechanical energy to electrical energy is called

(a) a transformer (b) a motor (c) a generator (d) a dipole

58. A transformer works because

(a) electricity is induced in a rotating coil (b) a changing magnetic field is created in the space surrounding the secondary coil (c) electricity flows from a primary coil to a secondary coil (d) electricity is inverted via the iron core

59. A step-up transformer

(a) increases voltage (b) decreases voltage (c) keeps voltage the same

60. The voltage across the primary coil of a transformer that has 100 turns is 10 V. What is the voltage across the secondary coil, which has 50 turns?

(a) 100 V (b) 50 V (c) 10 V (d) 5 V

For questions #61 - #64 use the following choices: (a) conduction (b) convection (c) radiation

61. Method of energy transfer that uses electromagnetic waves.

62. Method requiring direct contact. 63. Method primarily restricted to fluids.

64. Method that does not require a medium to move through.

65. Which of the following may not be shielded? (a) electrical fields (b) gravitational fields (c) magnetic fields

66. When is the strength of a field that is represented by filed lines the strongest?

(a) when the field lines are equidistant (b) when the field lines are close together (c) when the filed lines are far apart (d) none of these choices

67. As a system becomes more disordered, its entropy (a) increases (b) decreases (c) remains the same 68. Systems that are left alone move toward a state of (a) more entropy (b) less entropy (c) the same entropy 69. Entropy measures

(a) temperature (b) internal kinetic energy (c) disorder (d) potential energy

For Questions #70 - #74 use the following choices; (a) First Law of Thermodynamics

(b) Second Law of Thermodynamics (c) Third Law of Thermodynamics (d) Zeroth Law of Thermodynamics 70. Entropy is derived from this.

71. Two objects that are in thermal equilibrium with a third object, are in thermal equilibrium with each other. 72. Heat flows from hot to cold.

73. As the temperature of an object approaches zero, its entropy also approaches zero.

74. Whenever heat is added to a system, it is transformed to an equal amount of some other form of energy. 75. Which is an example of a heat engine?

(a) generator (b) electric motor (c) internal combustion engine (d) gyroscope

76. Hertz is a

(a) unit of period (b) unit of frequency (c) unit of wavelength (d) special radio wave

77. Just as "gravity" is the study of a wide range of gravitational interactions, "electrostatics" is the study of a wide range of

(a) electrical charges (b) electrical forces (c) electrical interactions (d) all of the above

78. . It is said that electric charge is conserved, which means that electric charge

(a) may occur in an infinite variety of quantities (b) is a whole number multiple of the charge of one neutron (c) will interact with neighboring electric charges (d) can be neither created nor destroyed (e) is sometimes negative

79. Two protons attract each other gravitationally and repel each other electrically. The stronger of these two forces is

(a) gravitation (b) electrical (c) neither of these Use the following choices for # 80 - # 85. Choices may be used more than once!

(a) amperes (b) volts (c) coulombs (d) ohms 80. Measure of electric potential.

81. Unit of charge. 82. Unit for flow of charge. 83. Unit for resistance. 84. Measures current. 85. “Push” behind current.

86. Conducting materials are composed of atoms with (a)) strong cohesive forces between them (b) loose outer electrons (c) excess neutrons compared with protons (d) vastly more charge than insulators

87. Before a thunder storm, clouds in the sky likely become

(a) conducting (b) polarized (c) grounded (d) a field-free region

88. Current in a conductor can be increased by (a) increasing the voltage across it (b) reducing its resistance (c) both of these (d) neither of these

89. On some early automobiles both headlights failed when one bulb burned out. The headlights were likely connected in

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90. Which of the following discovered that magnetism can create electric current

(a) Archimedes (b) Bernoulli (c) Faraday (d) Einstein

91. Fuses or circuit breakers must be inserted into a circuit in

(a) series (b) parallel (c) either

92. The source of all magnetism is

(a) tiny pieces of iron (b) tiny domains of aligned atoms (c) ferromagnetic materials (d) moving electric charge (e) none of the above

93. Whereas electric charges can be isolated, magnetic poles

(a) can also (b) cannot (c) gather in clusters (d) none of the above

94. A fan is operating on a circuit. A second fan is added in parallel to the first. The overall current in this parallel circuit will

95. When current reverses direction in a wire, the surrounding magnetic field

(a) also reverses direction (b) becomes momentarily stronger (c) contracts (d) expands

96. If a rod of iron is placed into the loops of a current-carrying wire then the resulting magnetic field (a) will be weaker (b) will be stronger (c) will remain the same (d) have greater energy

97. As the number of loops in a current carrying coil of wire increases, the magnetic field around that wire will (a) increase (b) decrease (c) remain the same

98. If the resistance in a wire is doubled and the voltage is also doubled then the current will

99. A refrigerator

(a)) produces cold (b) causes internal energy to disappear (c) transfers internal energy from inside to outside (d) transfers heat into cold (e)) none of the above

100. When you compress air with a tire pump, the air temperature in the tire

(a) increases (b) decreases (c) remains unaffected

Answer each of the following questions (#101 - #110) by selecting (a) for true and (b) for false.

101. The coldest temperature possible is 00_C. 102. Substances, which trap air are good insulators. 103.Gravitational forces are stronger than electrical forces.

104. All electrons are identical; each has exactly the same mass and charge.

105. It is possible to shield from electric charge and gravity.

106. Heat engines violate the Second Law of thermodynamics.

107. The sun may heat the Earth through convection. 108. Convection may cause winds to develop. 109. The embers that are remaining after a log has burned, may still heat you through electromagnetic waves.

110. All objects with any temperature radiate heat. Use the following choices to answer questions #111 – #120.

(a) electrostatics (b) charge (c) conductor (d) ion (e) semiconductor (ab) superconductor (ac) induction (ad) grounding (ae) insulator (bc) unit of charge 111.Conducts electricity without resistance. 112. A charged atom.

113. Attracting and repelling behavior are attributed to this.

114. Electricity at rest.

115. Electrons are free to roam throughout the material. 116. Will not conduct heat.

117. Sometimes conducts and sometimes insulates. 118. Coulomb.

119. When we allow charges to move off a conductor into the Earth.

120. Charging without contact.

For # 121 - #125 Use the following choices: (a) circuit (b) parallel circuit (c) series circuit (d) schematic diagram (e) electromagnet

121. A current carrying coil of wire with many loops. 122. The path that charges flow through.

123. A set of diagrams that can be used to describe a circuit.

124. A branched circuit.

125. A single pathway for charge to flow through. For questions #126 - #132 use the following choices: (a) capacitor (b) electric field (c) Amperage

(d) AC (e) DC (ab) Power (ac) Voltage

126. Rate at which energy is converted into another form 127. When the electrical charge moves in one direction only.

128. Stores electric potential. 129. Electric Pressure.

130. Electrical charge that flows in one direction and then reverses.

131. The space around an electric charge. 132. Moving charge.

Use the following choices to answer questions #133 – # 140.

(a) conduction (b) convection (c) insulator (d) radiation (e) absolute zero (ab) heat (ac) temperature

(ad) calorie

133. Temperature where no kinetic energy exists. 134. Energy that transfers from one object to another. 135. The quantity that tells how hot or cold something is when compared with a standard.

136. The quantity of heat required to raise the temperature of a unit of mass of the substance by 1 degree celsius.

137. Heat transfer by collisions.

138. Heat transfer by the movement of the hotter substance.

139. Heat transferred through electromagnetic waves. 140. An object that delays the transfer of heat.

141. Hot sand cools faster at night than does vegetation. Hence, the sand has

(a) a higher specific heat capacity (b) lower specific heat capacity (c) need more information

142. As the number of magnetic domains in a bar of iron increase, its likely hood of becoming a magnet will (a) increase (b) decrease (c) remain the same 143. An adiabatic process is one in which (a) no heat is added (b) no heat is removed (c) a substance’s internal mayenergy increases (d) a

substance’s internal energy may decrease (e) all of these 144. As a gas expands its internal energy will

(a) increase (b) decrease (c) remain the same 145. The most widely used temperature scale in the world

(a) Fahrenheit (b) Celcius (c) Kelvin (d) none of these

146. The amount of heat transferred to a system may be measure in

(a) calories (b) Joules (c) either of these (d) neither of these

147. Temperature is generally proportional to a substance’s

(a) thermal energy (b) specific heat capacity (c) conductivity (d) induction rate

148. The reason that water based fluids are usually utilized as coolants is because water has

(a) a high specific heat capacity (b) low specific heat capacity (c) no specific heat capacity

149. Heat engines, such as jet engines are most efficient when operating at

(a) high temperatures (b) low temperatures (c) any temperature

150. Compared with the power input, the power output of an ideal transformer is

(a) greater than (b) less than (c) the same as

Formulas:

P = IV V = IR Input Voltage = Output Voltage # turns in # turns out F = kq1q2

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PART 2. Use the Schematic to answer the following question. (5 points) Place your answer on the attached answer sheet.

Calculate the current displayed by the ammeter and the power consumed in the circuit shown. You must show all work and use proper significant figures to receive credit.

PART 3. Answer four (4) of the following five (5) questions. (5 points each) Place your answer on the attached answer sheet.

1. Draw a diagram of the electric field lines around two conductors which are oppositely charged and are 0.15 m from each other.

2. Calculate the magnitude of the electrostatic force between an electron and a proton located 1.5 x 10-6_{m apart. Is this an attractive or repulsive} force?

NOTE: qfundamental= 1.6 x 10-19_C k = 9.0 x 109_Nm2_/C2

3. A transformer has 3000 windings in the primary and 1500 windings in the secondary. If 125 volts exists at the input side of the transformer with a current of 15 amps what will be the output voltage and current?

4. Consider two charged objects. One carries a charge of 1.8 x 10-5_{C of charge. When the two are} separated by a distance of 0.9 m, there is a 2.7 N force between. What is the charge on the second object? k = 9.0 x 109_Nm2_/C2

5. An old electrical device is found in the closet of an abandoned barn. Its label indicates that it uses 8.5 W of power and 1.7 A of current. Part of the label is missing and the voltage rating cannot be

seen. What was the operating voltage of the device?

Scrap area:

48.0 V 12.0Ω

8.0 Ω

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JMJ

PHYSICS H SECOND TRIMESTER EXAM WRITTEN SECTION ANSWER SHEET NAME:_________________________________________

PART 2. Use the Schematic to answer the following question. 5 points

Calculate the current displayed by the ammeter and the power consumed in the circuit shown. You must show all work and use proper significant figures to receive credit.

PART 3: Answer one question in each box. Be sure to indicate which question you are answering.

PART 3: QUESTION #__________ PART 3: QUESTION #__________

48.0 V

12.0 Ω

8.0 Ω

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