MARKING GUIDE OF ADVANCED
LEVEL PHYSICS 2021 PAPER 2
LITTORAL PHYSICS TEACHERS' ASSOCIATION (LIPTA)
Presenters: Jill Baghoh & Mbah Oscar
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Question 1a
The force per unit length, F, between two current-carrying conductors kept a distance,
a, apart in a vacuum is suggested by an engineering student to be given by
Where
o
is the permeability of a vacuum. I
1
and I
2
are the currents in the conductors.
Determine whether the equation is homogenous or not.
1 2
2
o
I I
F
a
=
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Solution
Units of left-hand side = = kg s
-2
(N m
-1
accepted)
Units of = = kg m A
-2
s
-2
(from )
Substituting to come out with N A
-2
also accepted)
Therefore, units of left-hand side = = kg s
-2
(Or N m
-1
)
Units of left-hand side = units of right-hand side, hence equation is homogenous
2
kg m s
m
−
2
2
(kg m s ) m
A m
−
1 2
2
I I
F
l r
=
2 2 2
(kg m A s ) A
m
−−
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End of Document
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