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Page 1
MARKING SCHEME
PHYSICS
Subject Code – 042
CLASS – XII
Academic Session 2024 – 25
Maximum Marks:70 Time Allowed: 3hours
[SECTION – A]
Ans.1- (B) (1 mark)
VA> VB [VA = VC]
In the direction of electric field, the electric potential decreases.
Ans.2- (B) In the state of equilibrium, (1 mark)
The potential on the surface of bigger sphere = the potential at the surface of the smaller sphere
12
12
=
kq kq
rr
?
11
22
=
qr
qr
?
22
1 1 2 1 2 2
22
2 2 2 1
11
E
E
= = ? =
q r r r r
q r r
rr
Ans.3 - (C) (1 mark)
AtP2, B2 =
00
II
3 3
2
2
??
=
? ??
?
??
??
a a
AtP1, B1 =
( )
00
(I 4) I
2 2 4
??
=
?? aa
?
0
2
0 1
I
B 3
I B
4
? ??
??
?
??
=
? ??
??
?
??
a
a
?
2
1
B 4
B3
=
Ans.4 - (D)Sound waves as well as light waves (1 mark)
Ans.5 -(A) (1 mark)
Ans.6 - (C)When all the given components are connected(1 mark)
Page 2
MARKING SCHEME
PHYSICS
Subject Code – 042
CLASS – XII
Academic Session 2024 – 25
Maximum Marks:70 Time Allowed: 3hours
[SECTION – A]
Ans.1- (B) (1 mark)
VA> VB [VA = VC]
In the direction of electric field, the electric potential decreases.
Ans.2- (B) In the state of equilibrium, (1 mark)
The potential on the surface of bigger sphere = the potential at the surface of the smaller sphere
12
12
=
kq kq
rr
?
11
22
=
qr
qr
?
22
1 1 2 1 2 2
22
2 2 2 1
11
E
E
= = ? =
q r r r r
q r r
rr
Ans.3 - (C) (1 mark)
AtP2, B2 =
00
II
3 3
2
2
??
=
? ??
?
??
??
a a
AtP1, B1 =
( )
00
(I 4) I
2 2 4
??
=
?? aa
?
0
2
0 1
I
B 3
I B
4
? ??
??
?
??
=
? ??
??
?
??
a
a
?
2
1
B 4
B3
=
Ans.4 - (D)Sound waves as well as light waves (1 mark)
Ans.5 -(A) (1 mark)
Ans.6 - (C)When all the given components are connected(1 mark)
IR = IXC = IXL = 10V
XC = XL = R
Z =
22
CL
R (X X ) +-
Z =
22
R (R R) +-
Z = R
VS = IZ = IR = 10 V
So, the source voltage is also 10 V
When the capacitor is short circuited then
Z =
22
L
R (X ) +
= v?? 2
+ ?? 2
= ?? v2
VL = I ? XL =
10
R 5 2
2R
?= V
Ans.7 - (B)(1 mark)
Ans.8 - (B) The distance of closest approach(1 mark)
2
1
const
V
= d ...(1)
2
2
const
2
V
=
d
...(2)
From equations (1) and (2),
2
2
2
1
V
2
V
= ?V2 = 2 V1
? V2 = 2 V Given, (V1 = V)
Ans.9 - (C)(1 mark)
?? 2
?? -
?? 1
?? =
?? 2
- ?? 1
??
1 3 [1 3 2]
2[ 6] 6 v
-
-=
--
Page 3
MARKING SCHEME
PHYSICS
Subject Code – 042
CLASS – XII
Academic Session 2024 – 25
Maximum Marks:70 Time Allowed: 3hours
[SECTION – A]
Ans.1- (B) (1 mark)
VA> VB [VA = VC]
In the direction of electric field, the electric potential decreases.
Ans.2- (B) In the state of equilibrium, (1 mark)
The potential on the surface of bigger sphere = the potential at the surface of the smaller sphere
12
12
=
kq kq
rr
?
11
22
=
qr
qr
?
22
1 1 2 1 2 2
22
2 2 2 1
11
E
E
= = ? =
q r r r r
q r r
rr
Ans.3 - (C) (1 mark)
AtP2, B2 =
00
II
3 3
2
2
??
=
? ??
?
??
??
a a
AtP1, B1 =
( )
00
(I 4) I
2 2 4
??
=
?? aa
?
0
2
0 1
I
B 3
I B
4
? ??
??
?
??
=
? ??
??
?
??
a
a
?
2
1
B 4
B3
=
Ans.4 - (D)Sound waves as well as light waves (1 mark)
Ans.5 -(A) (1 mark)
Ans.6 - (C)When all the given components are connected(1 mark)
IR = IXC = IXL = 10V
XC = XL = R
Z =
22
CL
R (X X ) +-
Z =
22
R (R R) +-
Z = R
VS = IZ = IR = 10 V
So, the source voltage is also 10 V
When the capacitor is short circuited then
Z =
22
L
R (X ) +
= v?? 2
+ ?? 2
= ?? v2
VL = I ? XL =
10
R 5 2
2R
?= V
Ans.7 - (B)(1 mark)
Ans.8 - (B) The distance of closest approach(1 mark)
2
1
const
V
= d ...(1)
2
2
const
2
V
=
d
...(2)
From equations (1) and (2),
2
2
2
1
V
2
V
= ?V2 = 2 V1
? V2 = 2 V Given, (V1 = V)
Ans.9 - (C)(1 mark)
?? 2
?? -
?? 1
?? =
?? 2
- ?? 1
??
1 3 [1 3 2]
2[ 6] 6 v
-
-=
--
1 3 1 2 1
12 12 12 6 v
- - -
= + = =
?? = –6 cm
Ans.10 - (B)Diffraction (1 mark)
Ans.11- (A)doping level (1 mark)
Ans.12- (C)+0.4% (1 mark)
Ans.13- (A) (1 mark)
Ans.14- (A)(1 mark)
Ans.15- (D)(1 mark)
Ans.16- (A)(1 mark)
[SECTION – B]
Ans.17–
Given Ø
?? = ?? .???????? = ?? .???? × ?? .?? × ????
-????
??
?? = ?? .?? × ????
????
????
?? .?? .= ???? - Ø
?? =
????
?? ½
?? =
????
???? -Ø
?? ½
=
?? .???? × ????
-????
×?? ×????
?? ?? .???? × ????
-????
×?? .?? ×????
????
- ?? .???? ×?? .?? ×????
-????
½
=
???? .???? × ????
-????
?? .?? × ????
-????
(?? .???? - ?? .???? )
=
???? .???? × ????
-????
?? .?? ×????
????
= ???? .?? × ????
-?? ?? ½
Ans.18 - ?? 1
= 4 × 10
-7
?? ?? 2
= 6× 10
-7
??
Distance at which dark fringe is observed ?? = (?? +
1
2
)
????
?? ½
First Dark fringe for ?? 1
?? 1
=
1
2
4×10
-7
10
-2
?? = 2 × 10
-5
?? ½
Page 4
MARKING SCHEME
PHYSICS
Subject Code – 042
CLASS – XII
Academic Session 2024 – 25
Maximum Marks:70 Time Allowed: 3hours
[SECTION – A]
Ans.1- (B) (1 mark)
VA> VB [VA = VC]
In the direction of electric field, the electric potential decreases.
Ans.2- (B) In the state of equilibrium, (1 mark)
The potential on the surface of bigger sphere = the potential at the surface of the smaller sphere
12
12
=
kq kq
rr
?
11
22
=
qr
qr
?
22
1 1 2 1 2 2
22
2 2 2 1
11
E
E
= = ? =
q r r r r
q r r
rr
Ans.3 - (C) (1 mark)
AtP2, B2 =
00
II
3 3
2
2
??
=
? ??
?
??
??
a a
AtP1, B1 =
( )
00
(I 4) I
2 2 4
??
=
?? aa
?
0
2
0 1
I
B 3
I B
4
? ??
??
?
??
=
? ??
??
?
??
a
a
?
2
1
B 4
B3
=
Ans.4 - (D)Sound waves as well as light waves (1 mark)
Ans.5 -(A) (1 mark)
Ans.6 - (C)When all the given components are connected(1 mark)
IR = IXC = IXL = 10V
XC = XL = R
Z =
22
CL
R (X X ) +-
Z =
22
R (R R) +-
Z = R
VS = IZ = IR = 10 V
So, the source voltage is also 10 V
When the capacitor is short circuited then
Z =
22
L
R (X ) +
= v?? 2
+ ?? 2
= ?? v2
VL = I ? XL =
10
R 5 2
2R
?= V
Ans.7 - (B)(1 mark)
Ans.8 - (B) The distance of closest approach(1 mark)
2
1
const
V
= d ...(1)
2
2
const
2
V
=
d
...(2)
From equations (1) and (2),
2
2
2
1
V
2
V
= ?V2 = 2 V1
? V2 = 2 V Given, (V1 = V)
Ans.9 - (C)(1 mark)
?? 2
?? -
?? 1
?? =
?? 2
- ?? 1
??
1 3 [1 3 2]
2[ 6] 6 v
-
-=
--
1 3 1 2 1
12 12 12 6 v
- - -
= + = =
?? = –6 cm
Ans.10 - (B)Diffraction (1 mark)
Ans.11- (A)doping level (1 mark)
Ans.12- (C)+0.4% (1 mark)
Ans.13- (A) (1 mark)
Ans.14- (A)(1 mark)
Ans.15- (D)(1 mark)
Ans.16- (A)(1 mark)
[SECTION – B]
Ans.17–
Given Ø
?? = ?? .???????? = ?? .???? × ?? .?? × ????
-????
??
?? = ?? .?? × ????
????
????
?? .?? .= ???? - Ø
?? =
????
?? ½
?? =
????
???? -Ø
?? ½
=
?? .???? × ????
-????
×?? ×????
?? ?? .???? × ????
-????
×?? .?? ×????
????
- ?? .???? ×?? .?? ×????
-????
½
=
???? .???? × ????
-????
?? .?? × ????
-????
(?? .???? - ?? .???? )
=
???? .???? × ????
-????
?? .?? ×????
????
= ???? .?? × ????
-?? ?? ½
Ans.18 - ?? 1
= 4 × 10
-7
?? ?? 2
= 6× 10
-7
??
Distance at which dark fringe is observed ?? = (?? +
1
2
)
????
?? ½
First Dark fringe for ?? 1
?? 1
=
1
2
4×10
-7
10
-2
?? = 2 × 10
-5
?? ½
First Dark fringe for ?? 2
?? 2
=
1
2
6×10
-7
10
-2
?? = 3 × 10
-5
??
First dark fringe will be the distance where both dark fringes will coincide i.e LCM of ?? 1
&?? 1
½
i.e. 2 × 10
-5
?? × 3 × 10
-5
??
= 6 × 10
-5
?? ½
OR
(II) ?????? ?? = ?? 1
+ ?? 2
+ 2v?? 1
v?? 2
cos? 0.5 M
Since, ?? 1
= ?? 2
= ??
Net I = I + I + 2 I cos?
= 2I (1 + cos?)
= 2I (2 cos
2
Ø
2
) 0.5 M
For path difference ?/4 , phase difference is p/2 0.5 M
Net I = 4 I cos
2
?? 4
Net I = 2 I 0.5 M
(2 Marks)
Ans.19 - (I)The direction of the magnetic field is perpendicular and inward into the plane of thepaper 0.5M
(II) For a head-on collision to take place, the radius of the path of each ion should be equal to 0.5
m.
0.5
mv
r
qB
== m 0.5M
26 5
19
4 10 2.4 10
B
4.8 10 0.5
mv
qr
-
-
? ? ?
==
??
0.5M
B = 0.04 T 0.5M
For VI Candidate
(a) As Pitch (p)=
2????? ?????? O
????
0.5M
Or, p=
2 ?? 3.14 ?? 1.7?? 10
-27
?? 2 ?? 10
5
?????? 30
0
1.6 ?? 10
-19
?? 1.5
m
Or, P=7.7X10
-3
m 0.5M
(b)As, done by magnetic field is always zero K.E=1/2mv
2
0.5M
KE=3.4 X 10
-17
J 0.5M
Ans.20 –(i) Nuclear fission –W
0.5M
Reason: As W has binding energy per nucleon less then Y and X and nucleus is larger
in size.
0.5M
Page 5
MARKING SCHEME
PHYSICS
Subject Code – 042
CLASS – XII
Academic Session 2024 – 25
Maximum Marks:70 Time Allowed: 3hours
[SECTION – A]
Ans.1- (B) (1 mark)
VA> VB [VA = VC]
In the direction of electric field, the electric potential decreases.
Ans.2- (B) In the state of equilibrium, (1 mark)
The potential on the surface of bigger sphere = the potential at the surface of the smaller sphere
12
12
=
kq kq
rr
?
11
22
=
qr
qr
?
22
1 1 2 1 2 2
22
2 2 2 1
11
E
E
= = ? =
q r r r r
q r r
rr
Ans.3 - (C) (1 mark)
AtP2, B2 =
00
II
3 3
2
2
??
=
? ??
?
??
??
a a
AtP1, B1 =
( )
00
(I 4) I
2 2 4
??
=
?? aa
?
0
2
0 1
I
B 3
I B
4
? ??
??
?
??
=
? ??
??
?
??
a
a
?
2
1
B 4
B3
=
Ans.4 - (D)Sound waves as well as light waves (1 mark)
Ans.5 -(A) (1 mark)
Ans.6 - (C)When all the given components are connected(1 mark)
IR = IXC = IXL = 10V
XC = XL = R
Z =
22
CL
R (X X ) +-
Z =
22
R (R R) +-
Z = R
VS = IZ = IR = 10 V
So, the source voltage is also 10 V
When the capacitor is short circuited then
Z =
22
L
R (X ) +
= v?? 2
+ ?? 2
= ?? v2
VL = I ? XL =
10
R 5 2
2R
?= V
Ans.7 - (B)(1 mark)
Ans.8 - (B) The distance of closest approach(1 mark)
2
1
const
V
= d ...(1)
2
2
const
2
V
=
d
...(2)
From equations (1) and (2),
2
2
2
1
V
2
V
= ?V2 = 2 V1
? V2 = 2 V Given, (V1 = V)
Ans.9 - (C)(1 mark)
?? 2
?? -
?? 1
?? =
?? 2
- ?? 1
??
1 3 [1 3 2]
2[ 6] 6 v
-
-=
--
1 3 1 2 1
12 12 12 6 v
- - -
= + = =
?? = –6 cm
Ans.10 - (B)Diffraction (1 mark)
Ans.11- (A)doping level (1 mark)
Ans.12- (C)+0.4% (1 mark)
Ans.13- (A) (1 mark)
Ans.14- (A)(1 mark)
Ans.15- (D)(1 mark)
Ans.16- (A)(1 mark)
[SECTION – B]
Ans.17–
Given Ø
?? = ?? .???????? = ?? .???? × ?? .?? × ????
-????
??
?? = ?? .?? × ????
????
????
?? .?? .= ???? - Ø
?? =
????
?? ½
?? =
????
???? -Ø
?? ½
=
?? .???? × ????
-????
×?? ×????
?? ?? .???? × ????
-????
×?? .?? ×????
????
- ?? .???? ×?? .?? ×????
-????
½
=
???? .???? × ????
-????
?? .?? × ????
-????
(?? .???? - ?? .???? )
=
???? .???? × ????
-????
?? .?? ×????
????
= ???? .?? × ????
-?? ?? ½
Ans.18 - ?? 1
= 4 × 10
-7
?? ?? 2
= 6× 10
-7
??
Distance at which dark fringe is observed ?? = (?? +
1
2
)
????
?? ½
First Dark fringe for ?? 1
?? 1
=
1
2
4×10
-7
10
-2
?? = 2 × 10
-5
?? ½
First Dark fringe for ?? 2
?? 2
=
1
2
6×10
-7
10
-2
?? = 3 × 10
-5
??
First dark fringe will be the distance where both dark fringes will coincide i.e LCM of ?? 1
&?? 1
½
i.e. 2 × 10
-5
?? × 3 × 10
-5
??
= 6 × 10
-5
?? ½
OR
(II) ?????? ?? = ?? 1
+ ?? 2
+ 2v?? 1
v?? 2
cos? 0.5 M
Since, ?? 1
= ?? 2
= ??
Net I = I + I + 2 I cos?
= 2I (1 + cos?)
= 2I (2 cos
2
Ø
2
) 0.5 M
For path difference ?/4 , phase difference is p/2 0.5 M
Net I = 4 I cos
2
?? 4
Net I = 2 I 0.5 M
(2 Marks)
Ans.19 - (I)The direction of the magnetic field is perpendicular and inward into the plane of thepaper 0.5M
(II) For a head-on collision to take place, the radius of the path of each ion should be equal to 0.5
m.
0.5
mv
r
qB
== m 0.5M
26 5
19
4 10 2.4 10
B
4.8 10 0.5
mv
qr
-
-
? ? ?
==
??
0.5M
B = 0.04 T 0.5M
For VI Candidate
(a) As Pitch (p)=
2????? ?????? O
????
0.5M
Or, p=
2 ?? 3.14 ?? 1.7?? 10
-27
?? 2 ?? 10
5
?????? 30
0
1.6 ?? 10
-19
?? 1.5
m
Or, P=7.7X10
-3
m 0.5M
(b)As, done by magnetic field is always zero K.E=1/2mv
2
0.5M
KE=3.4 X 10
-17
J 0.5M
Ans.20 –(i) Nuclear fission –W
0.5M
Reason: As W has binding energy per nucleon less then Y and X and nucleus is larger
in size.
0.5M
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