Qn.120
NOR gate output is followed by two inverter because NAND gate is connected as inverter.
Hence equivalent circuit is NOR gate
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Qn.121
Magnetic field induction B at centre of loop of radius R is given as
.................... (1)
where I is current in the loop and μo is the permeability of free space .
When helium nucleus that has charge 2e is moving with speed v in a circular loop ,
current I = ( 2e v ) = ( 2e ) × [ ( 2 π R ) / T ] ....................(2)
where T = 2 s is period of revolution
If we substitute current I using eqn.(2) , we get magnetic field from eqn.(1) as
T
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Qn.122
Magnetic field at centre of loop has two parts , (i) one part due to long wire carrying current I and
(ii) second part due to current I in circular loop
Magnetic field due to long wire , 
Magnetic field due to circular loop , 
Net magnetic field , 
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Qn. 123
Let charge on particle-X = q and charge on particle-Y = 2q
Kinetic energies of particles after accelerated by same potential difference V is given as
.................... (1)
....................(2)
From above equations (1) and (2) , we get
......................(3)
In magnetic field , magnetic force equals centripetal force . Hence we have
...........................(4)
........................ (5)
From above equations (4) and (5) we get
....................(4)
By equating eqn.(3) and (4) , after simplification, we get 
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