1). The working principle of transformer depend on
a) Coulombs law.
b) Faradays law of electromagnetic induction.
c) Amperes law
d) Newtons law
2). Addition of 0.3% to 4.5% silicon to iron
a) increase the electrical resistivity of iron
b) reduces the saturation magnetization.
c) increases hysteresis loss
d) non of the above
4). A laminated iron core has reduced eddy current losses because
a) more wire can be used with less dc resistance in coil
b) The lamination are insulated from each other
c) The magnetic flux is concentrated i
d) The lamination are stacked vertically.
4). Lamination of core are generally made of
a) case iron.
c) silicon steel.
d) stainless steel
5).The primary and secondary windings of a transformer are of the
a) conductivily linked
b) inductively linked
c) electrically linked
d) mechanically linked
6). In a core type transformer
a) HV winding placed near to the core limb
b) LV winding placed near to the core limb
c) any of the LV or HV can be placed near to the core limb
d) HV and LV winding are placed in different core limbs
7). At what power factor , the voltage regulation of a transformer can be zero ?
a) lagging power factor
b) leading power factor
c) unity power factor
d) zero power factor
8). A single phase transformer has its maximum efficiency at 60 percent of full load. At full load copper loss will be
a) Equal to care loss
b) Less then core loss
c) More then core loss
9) Thin laminations are used in a machine in order to reduce
a) Eddy current losses
b) hysteresis losses
c) Both 1 and 2
d) Copper losses
10) Auto transformer makes effective saving on copper and copper losses, when its transformation ration is equal to
a) Very low
b) Less then one
c) Greater then one
d) Approx to one