EE part 1
mutual inductance and self inductance of the two coils
The coefficient of coupling between two air core coils depends on
N(theta) / I
The coefficient of self-inductance of a coil is defined as
the temperature should remain constant
The condition in Ohm's law is that
the degree of magnetic linkage
The coupling coefficient denotes
yeap
The current carrying capacity of the fuse material depends on length, material and cross-sectional area?
linear
The curve representing Ohm's law is that
it does not affect the constant direct current
The effect of the inductance of a coil on a constant direct current is that
False
The flux linked with a coil of inductance L carrying current i is d/dt (Li)
in inverse proportion to the square of the distance
The force between two magnetic poles varies with distance between them. The variation is
exponential law
The growth of current in an inductive circuit follows
Lenz
The law that induces emf and current always opposes the cause producing them was discovered by
current, magnetic field and direction of force on a conductor
The left hand rule correlates
G1 + G2 + G3
Three elements having conductance G1, G2 and G3 are connected in parallel. Their combine conductance will be
soft iron
A material commonly used for shielding or screening magnetism is
lodestone
A natural magnet is called
tends to oppose the decay of coil current
A collapsing field around the coil
zero
A conductor of length L has current I passing through it, when it is placed parallel to a strong magnetic field. the force experienced by the conductor will be
demagnetizing metallic part
A degaussing is the process of
nickel, cobalt and steel
A magnet is able to attract
4 ohms
A resistance of 4 ohms is connected across 100 volt supply. When another resistor is connected in parallel with 4 ohms, the total current taken from supply was found to be 50A. The value of resistance R is
8.854 x 10^-12 farad/meter
Absolute permittivity of vacuum is taken as
always opposes the cause producing it
According to Lenz's law the direction of induced emf and hence current
B^1.6
According to hysteresis law, hysteresis loss in a material is proportional to
core saturation
Air gap in the iron core of an inductor prevents
seen or touched
An electric current can neither be
K = M / square root of L1l2
Coupling coefficient k, a term much used in radio work can be obtained from
curie temperature
Each ferromagnetic material has characteristic temperature above which its properties are quite different from those below that temperature. This temperature is called
increasing the resistance of magnetic medium
Eddy current loss can be minimized by
1/2 LI^2 joules
Energy stored in an inductance is given by
north to south
Externally, magnetic line of force travels
semiconductor
Ferrimagnetic materials generally behave as a
resistor R4
Four resistances R1, R2, R3, R4 are connected in series against 220 V supply. The resistances are such that R1 > R2 > R3 > R4. The least power consumption will be in
inductance of the coil
Good smoothing factor of a coil depends on the
vacuum cleaner
Heating effect of current has undesirable side effect in
using grain oriented silicon steel
Hysteresis loses can be reduced by
is always constant
In a parallel circuit the potential difference across the resistance
constant
In a series circuit the current
eddy current loss
In electrical machines, laminated cores are used with a view of reducing
direction of force on conductor
In the left hand rule, thumb always represents
paramagnetic material
Interaction between the neighboring dipoles is negligible in case of a
a column of mercury
International ohm is defined in terms of resistance of
near to one end of a magnet
Iron becomes magnetized by induction when its
low permeability
It is difficult to magnetize steel because it is
the square of the current.
It was experimentally found by James Prescott Joule that the heat produced in a current-carrying conductor is proportional to
4.2 Joules per calories
Joule's mechanical equivalent of heat, J, is equal to
more than unity
Leakage factor is
flux
Magnetic lines of force are called
A voltage source and a conductor
Minimum requirements to cause the flow of current.
M = N2 (dtheta) / dt
Mutual Inductance can also be defined as
semiconductor
Ohm's Law does not apply to
electrolytes
Ohm's law can be applied with certain reservations to
nawp
Ohm's law is applicable to electric arc, gas discharge lamps and rectifying devices?
conductance
Permeance is analogous to
1 + k/µo
Relative permeability of a material is given by (K is susceptibility of the material)
Its length increases.
Resistance of a conductor increases when
wire wound resistors
Resistors commonly used in power circuits
inductance
Sparking occurs when a load is switched off because the circuit has high
The resistance of conductor is the hindrance by which the conductor opposes the flow of current.
Statement that is correct.
increase in resistance per ohm per degree centrigade
Temperature coefficient of a conductor is defined as the
J / m^3 / s
The area of hysteresis loop represents hysteresis loss in
Graphite
The best conductor of electricity.
soft magnetic materials
The magnetic materials which can be easily magnetized in both directions are known as
M.M.F
The magnetic potential in a magnetic circuit can be measure in terms of
residual
The magnetism that remains in a magnet after the magnetizing force has been removed is called
electrons orbital motion, spin of the nucleus about its axis and electron spin
The magnetization in any magnetic material appears as a result of
touching each other
The mutual inductance of two coils is maximum when the coils are
the conductivity of a material for magnetic lines of force
The permeability of a material means
effects produced
The presence of an electric current is made known by
heating, magnetic and electric shock
The presence of the current is only made known by the effect produces. Three important effects are
B / µoH
The relative permeability (µr) is given by
slightly greater than 1
The relative permeability of paramagnetic substance is
5000
The relative permeability µ for iron is
1:4
The resistance R1 and R2 are connected in parallel. The ratio of values of resistance R1:R2 is 4:1. The currents in R1:R2 will be equal to
increases
The resistance of carbon when its temperature is decreased
The nature of the material of the conductor only.
The specific resistance p depends upon
resistance of a conductor which has a length of 1m and cross section of 1m squared at 20 degrees celcius
The specific resistance p is defined as
magnetization
The sum of the magnetic moments in unit volume of the solid is called
L/R
The time constant of an inductive circuit is defined as the ratio of
63% of its final steady state value
The time constants is the time it takes the current in an inductive circuit to rise to
Square root of L1L2
The value of mutual inductance in term of self inductance of the two coils L1 and L2 is proportional to
4π x 10^-7 Hm^-1
The value of permeability for the free space is
75%
The voltage applied across an electric press was reduced by 50%. The power consumed by the press will be reduced by
ferrites
Transformer cores operating at microwave frequency ranges are generally made up of
3:1
Two electric presses are connected in parallel. The resistance of the first press is 100 ohms and that of the second is 300 ohms. The total current taken by both the presses is 4A. The ratio of current taken by first: second will be equal to
a force
Voltage applied across a circuit acts as
of interatomic collision
When current flows in a conductor, heat is produced because
resistance of heater coil is more than that of supply wires
When current flows through heater coil it glows but supply wiring does not glow because
Increases
When its temperature is increased, the resistance of a conductor
True
When steel torodial ring is magnetized by passing current through its coil, it develops no magnetic poles
magnetic flux density = flux / area
When the magnetic flux and the area under its influence are known, the magnetic flux density can be given as
Faraday's Law
Whenever a conductor cuts magnetic flux, an emf is induced in that conductor. This statement is due to
thermistor
Which of the following has negative coefficient of resistance?
supermalloy
Which of the following has the highest value of relative permeability
Coefficient of coupling for tightly coupled coil is zero
Which of the following is correct?
magnetic field intensity
Which of the following is vector quantity
carbon steel, platinum cobalt and alnico v
Which of the following material is used for making permanent magnets
diamagnetic
Which of the following materials does not have permanent magnetic dipole
Inductance characterizes the magnetic properties of a coil which are significant for the value of self induced voltage generated due to current change in the coil.
Which of the following statements about inductance of a coil is true?
current
While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electric circuit?
flux and current flow
While comparing magnetic and electric circuits, the point of dissimilarity exists while considering