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JEE Main Physics Class 12 Moving Charges and Magnetism Part 1 Questions
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© examsnet.com
Question : 1
Total: 100
A proton, an electron, and a Helium nucleus, have the same energy. They are in circular orbits in a plane due to magnetic field perpendicular to the plane. Let
r
p
,
r
e
and
r
H
e
be their respective radii, then,
[10 April 2019, I]
r
e
>
r
p
=
r
H
e
r
e
<
r
p
=
r
H
e
r
e
<
r
p
<
r
H
e
r
e
>
r
p
>
r
H
e
Validate
Solution:
As
m
v
r
=
q
v
B
⇒
r
=
m
v
q
B
=
√
2
m
K
.
E
q
B
[
As
:
1
2
m
v
2
=
K
.
E
.
⇒
m
2
v
2
=
2
m
K
.
E
⇒
m
v
=
√
2
m
K
.
E
.
]
For proton, electron and
α
-particle,
m
H
e
=
4
m
p
and
m
p
>
>
m
e
Also
a
H
e
=
2
q
p
and
q
p
=
q
e
∴
As
K
E
of all the particles is same then,
r
α
√
m
q
∴
r
H
e
=
r
p
>
r
e
© examsnet.com
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