Terms in this set (14)

  • D
    In which case or cases is electric field present? I. A spark jumping between two nearby rods. II. A charge that is momentarily at rest. III. A rotating bar magnet. a. I only b. I and II only c. II and III only d. I, II and III
  • C
    In which case can a magnetic field be produced? a. A charged comb. b. A falling glass rod. c. A welder's arc flash. d. A rolling plastic cylinder.
  • D
    Which device can be used to determine the polarity of an unmarked magnet? a. a charged glass stirring rod b. a gold-leaf electroscope c. a sprinkle of iron filings d. an improvised compass
  • A
    How will you describe the magnetic field around a straight current-carrying wire? a. The magnetic field is strongest near and around the wire. b. The magnetic field consists of straight lines parallel to the wire. c. The magnetic field does not vary with the distance from the wire. d. The magnetic field gets stronger with increasing distance from the wire.
  • B
    Which statement about an electromagnet is TRUE? a. The electric field surrounding a battery-powered electromagnet alternates constantly. b. The current in the electromagnet coil temporarily magnetizes the iron core. c. The electric field strength is inversely proportional to the current. d. The magnetic field lines produced are all straight.
  • C
    What can be inferred from the alignment of compass needles in the set-up below? a. A permanent magnet is nearby. b. The power switch was turned off for long. c. The current-carrying coil becomes magnetic. d. There is a constant and uniform magnetic field around the coil.
  • B
    As part of a traffic light system, large loops of wire are buried beneath road intersections. Which of the statements is NOT TRUE about the operation of this traffic light system? a. Vehicles driven over the buried coils activate a traffic light sensor. b. The conducting loops activate a color-dependent field. c. The alternating current sent through the buried coils produce an electromagnetic field in each coil. d. A fixed number of vehicles over the coils can trigger the traffic light to change green.
  • C
    Complete the following statement: Moving a metallic detector past a 5 peso coin creates a secondary magnetic field that is most likely that of _____. a. a horse shoe magnet b. a flat refrigerator magnet c. a current-carrying, circular loop d. a V-shaped straight wire that carries a current
  • C
    During the Student Technologists and Entrepreneurs of the Philippines (STEP) Competition in Landscaping, a water pond transformer changes 216 V across the primary to 12 V across the secondary. If the secondary coil has 10 turns, how many turns does the primary coil have? a. 10 turns b. 18 turns c. 180 turns d. 228 turns
  • D
    What basic principle enables ALL electric motors to operate? a. Iron is the only element that is magnetic. b. Opposite electric charges attract and like charges repel. c. A moving conductor within a magnetic field will experience an electromotive force. d. A current-carrying conductor placed within a magnetic field will experience a magnetic force.
  • D
    A magnet moves inside a coil. Consider the following factors: I. strength of the magnet II. number of turns in the coil III. speed at which the magnet moves Which can affect the electromotive force (emf) induced in the coil? a. I only b. II only c. III only d. All three factors
  • D
    Which statement about transformers is FALSE? a. A step-down voltage transformer steps up the current. b. Transformers use mutual induction. c. Transformers are an application of Faraday's and Lenz's Laws. d. A transformer can function with either an alternating current (AC) or a steady direct current (DC).
  • A
    What transformation can take place in an improvised generator? a. mechanical energy into electrical energy b. electrical energy into mechanical energy c. alternating current into direct current d. direct current into alternating current
  • B
    A loop of conductor lies flat on a horizontal table. A toy magnet is hanging still over it with the magnet's north-seeking pole pointing down. What happens next? a. The magnet produces a clockwise current in the coil. b. The magnet does not produce any current in the coil. c. The magnet produces an upward electromagnetic current. d. The magnet produces a counterclockwise current in the coil.