Multiple Choice QuestionsIn a discharge tube ionization of enclosed gas is produced due to collisions between
positive ions and neutral atoms/molecules
negative electrons and neutral atoms/molecules
photons and neutral atoms/molecules
photons and neutral atoms/molecules
A coil of inductive reactance 31 Ω has a resistance of 8Ω. It is placed in series with a condenser of capacitative reactance 25Ω. The combination is connected to an a.c. soruce of 110 V. The power factor of the circuit is
0.56
0.64
0.80
0.80
Power dissipated across the 8 Ω resistor in the circuit shown here is 2W. The power dissipated in watt units across the 3 Ω resistor is
2.0
1.0
0.5
0.5
D.
0.5
Resistances 
and 
are connected in series, so effective resistance
Now, R' and 
are in parallel. We know that potential difference across resistances in parallel order is same.
Hence, 
or 
or 
or 
...(i)
Power dissipated across 
resistance is
Power dissipated across 
resistance is
but 
Kirchhoff's first and second laws for electrical circuits are consequences of
conservation of energy
conservation of electric charge and energy respectively
conservation of electric charge
conservation of electric charge
Above Curie temperature
a ferromagnetic substance becomes paramagnetic
a paramagnetic substance becomes diamagnetic
a diamagnetic substance becomes paramagnetic
a diamagnetic substance becomes paramagnetic
An electric dipole of moment 
is lying along a uniform electric field 
The work done in rotating the dipole by 
2pE
2pE
A parallel plate air capacitor is charged to a potential difference of V volts. After disconnecting thecharging battery the distance between the plates of the capacitor is increased using an insulating handle. As a result the potential difference between the plates
decreases
does not change
becomes zero
becomes zero
A square surface of side L m is in the plane of the paper. A uniform electric field 
, also in the plane of the paper, is limited only to the lower half of the square surface, (see figure). The electric flux in SI units associated with the surface is
zero
zero
The binding energy of deuteron is 2.2 MeV and that of 
is 28 MeV. If two deuterons are fused to form one 
then the energy released is
25.8 MeV
23.6 MeV
19.2 MeV
19.2 MeV
In a radioactive material the activity at time t1 is R1 and at a later time t2, it is R2. If the dacay constant of the material is λ, then
R1 = R2 e-λ(t1 -t2 )
R1 = R2 eλ(t1 -t2 )
R1 = R2 e(t2 /t1 )
R1 = R2 e(t2 /t1 )
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