Homework help/:

Discussion in 'Homework Help' started by jacyhui, May 26, 2008.

  1. jacyhui

    Thread Starter New Member

    May 26, 2008

    1. What is the disadvantage of using contact brushes in an a.c generator?
    a emf generated is very much reduced
    b heat oss through brushes very high
    c current drawn from the generator would be small
    d sparks will appear at the contact

    2. A step up transformer is used to...
    a low potential energy to high
    b low current to high
    c direct current to alternating
    d low to high power

    3. the primary coil of an ideal step up transformer is connected to a low dc source. what will appear at the secondary coil?
    a high potential energy
    b high potential a.c.
    c no power
    d low current a.c

    4. what is the material used to make the core of an ideal transformer?
    a aluminium
    b iron
    c copper
    d stainless steel

    5 what is true of an ideal step-down transformer?
    a the power of pri coil is teh same as power at sec coil
    b the power is higher the the pri coil
    c the power is higher at the sec coil
    d the power of the sec coil is not dependent on the power at the pri coil

    please help me):
    i missed out a few phy lessons because i was down with some flu.
    so if possible, do offer some explanations with the answer so i can understand:)
  2. thingmaker3

    Retired Moderator

    May 16, 2005