CBSESolved Test Papers
PHYSICSClass XII
Chapter : Magnetic Effects of Current and Magnetism
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CBSE TEST PAPER-05
CLASS - XII PHYSICS (Magnetic Effects of Current and Magnetism)
1. What type of magnetic material is used in making permanent magnets? [1]
2. Which physical quantity has the unit wb/m2? Is it a scalar or a vector quantity? [1]
3. Define angle of dip. Deduce the relation connecting angle of dip and horizontal
component of earth’s total magnetic field with the horizontal direction.
[2]
4. A point change +q is moving with speed
perpendicular to the magnetic field B as shown
in the figure. What should be the magnitude and
direction of the applied electric field so that the
net force acting on the charge is zero?
[2]
5. The energy of a charged particle moving in a uniform magnetic field does not
change. Why?
[2]
6. In the figure, straight wire AB is fixed; white the
loop is free to move under the influence of the
electric currents flowing in them. In which
direction does the loop begin to move? Justify.
[2]
7. State two factors by which voltage sensitivity of a moving coil galvanometer
can be increased?
[2]
8. The current sensitivity of a moving coil galvanometer increases by 20% when
its resistance is increased by a factor of two. Calculate by what factor, the
voltage sensitivity changes?
[3]
9. (a) Show how a moving coil galvanometer can be converted into an ammeter?
(b) A galvanometer has a resistance 30 and gives a full scale deflection for a
current of 2mA. How much resistance in what way must be connected to
convert into?
(1) An ammeter of range 0.3A
(2) A voltammeter of range 0.2V.
[5]
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CBSE TEST PAPER-05
CLASS - XII PHYSICS (Magnetic Effects of Current and Magnetism)
[ANSWERS]
Ans 1: Material having high coercivity is used in making permanent magnets.
Ans 2: Magnetic field. It is a vector quantity.
Ans 3: cosBH
B
sin
sin
cos
BV
B
BV B
B BH
Ans 4: Force on the charge due to magnetic field = qVB sin
Since isB to the plane of paper and in words
F = qVB sin 90o
F = qVB (along OY)
Force on the charge due to electric field
F = qE
Net force on change is zero if qE = qVB
(along YO)
Ans 5: The force on a charged particle in a uniform magnetic field always acts in a
direction perpendicular to the motion of the charge. Since work done by the
magnetic field on the charge is zero, hence energy of the charged particle will not
change.
Ans 6: Since current in AB and arm PQ are in same direction therefore wire will attract
the arm PQ with a force (say F1)
But repels the arm RS with a force (say F2)
Sine arm PQ is closer to the wire AB
F1 > F2 i.e. the loop will move towards the wire.
BVTan
BH
E = VB
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Ans 7: Voltage sensitivity = nBA
kR
It can be increased by
(1) increasing B using powerful magnets
(2) decreasing k by using phosphor borne strip
Ans 8: Current sensitivity ( )nBA
iI k
Voltage sensitivity ( )nBA
iiV kR
Resistance of a galvanometer increases when n and A are changed
Given R = 2R
Then n = n and A = A
New current sensitivity
' ' '( )
'
n A Biii
I k
New voltage sensitivity
' ' ' '( )
' ' 2
n A Biv
V I R kR
' 120( )
' 100Since v
I I
From (i) and (iii)
' ' 120
100
' ' 120
100
n A B
R I
n A B nAB
k k
Using equation (iv)
' 6
5 2
' 3
5
nAB
V kR
nAB
V kR
Thus voltage sensitivity decreases by a factor of 3
5.
Ans 9: (a) A galvanometer can be converted into an
ammeter by connecting a low resistance
called shunt parallel to the
galvanometer.
Since G and RS are in parallel voltage
across then is same IgRG = (I – Ig) RS
n’A’=6
5nA
' 3
5V V
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(b) (1) I = 0.3A G = 30 Ig = 2mA = 210-3 A
Sheent (S) = IgG
I Ig
3
3
2 10 30
(0.3 2 10 )S
(2) G = 30 , Ig = 2mA = 210-3A, V = 0.2V
Shunt Resistance (R) V
GIg
3
0.230
2 10R
G
IgRs R
I Ig
S = 0.2
R = 70
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