CBSE Class 12 Physics Previous Year Question Paper Term 1 2021 SSJ-1-Set-4
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SECTION – A
This section consists of 25 multiple choice questions with over tilt choice to attempt any 20 questions. In case more than desirable number of questions are attempted, only first 20 questions will be considered for evaluation.
An electric dipole placed in a non-uniform electric field will experience:
- Only a force
- Only a torque
- both force and torque
- Neither force nor torque
Let NI be the number of electric field lines going out of an imaginary cube of side that encloses an isolated point charge 2q and N2 be the corresponding number for an imaginary sphere of radius that encloses an isolated point charge 3q. Then (N1/N2) is:
In the circuit given below P ≠ R and the reading of the galvanometer is same with Switch S open or closed. Then:
- IQ = IR
- IR =IG
- IP = IG
- IQ = IG
Two wires A and B, of the same material having length in the ratio 1: 2 and diameter in the ratio 2: 3 are connected in series with a battery. The ratio of the potential differences (VA/ VB) across the two wires respectively is:
- 5 : 7
- 7 : 5
- 1 : 1
- the number of turns in the inductor is increased
- the separation between the plates of the capacitor is increased
- an iron rod is introduced into the inductor
- a dielectric is introduced into the gap between the plates of the capacitor
- 150 V
- 175 V
- 220 V
- 250 V
- a resistance of 105 Ω
- a resistance of 107 Ω
- a resistance of ∞ resistance
- a gap only
- 122 J
- 270 J
- 420 J
- 720 J
- 1.2 μT, vertically upward
- 1.2 μT, vertically downward
- 0.6 μT, vertically upward
- 0.6 μT, vertically downward
- 104 V
- 103 V
- 102 v
- 10 v
- 10 Ω
- 7 Ω
- 3 Ω
- 2 Ω
An electron is projected with velocity along the axis of a current carrying long solenoid. Which one of the following statements is true?
- The path of the electron will be circular about the axis.
- The electron will be accelerated along the axis.
- The path of the electron will be helical.
- The electron will continue to move with the same velocity along the axis of the solenoid.
If the speed v of a charged particle moving in a magnetic field ( is perpendicular to ) is halved, then the radius of its path will:
- not change
- become two times
- become one- fourth
- become half
- It is placed in a space varying magnetic field that does not vary with time.
- A direct current is passing through the plate.
- An alternating current is passing through the plate.
- It is placed in a time varying magnetic field.
- 6 × 106 ms-1
- 3 × 106 ms-1
- 4 × 105 ms-1
- 2 × 103 ms-1
- A current carrying conductor
- A moving charge
- A stationary charge
- A rectangular current loop with its parallel to the felid
- 8 L
- 6 L
- 4 L
- 2 L
- both A and B
- neither A nor B
- 10.60 × 10-8 Ω-m
- 8.32 × 10-8 Ω-m
- 7.61 × 10-8 Ωm
- 5.45 × 10-8 Ωm
- 50 Hz
- less if the length of the wire is increased
- more if the length of the wire is increased
- more if a wire of steel of same dimension is used
- more if the temperature of wire is increased
- P and R only
- Q and R only
- P and Q only
- P, Q and R
- 3 B0
- 9 B0
- An inductor has infinite resistance in a dc circuit.
- A inductor and a capacitor both cannot conduct in a dc circuit.
- A capacitor can conduct in a dc circuit but not an inductor.
- An iductor can conduct in a dc circuit but not a capacitor.
- 53 V
- 43 V
- intensity of the electric field increases
- intensity of the electric field decreases
- work is done by the electric field
- work is done by the external source
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
- Assertion (A) is true, but Reason (R) is false.
- Assertion (A) is false, but Reason (R) is true.
This section consists of 6 multiple choice questions with an overall choice to attempt any 5 questions. In case more than the desirable number of questions are attempted, only the first 5 questions will be considered for evaluation.
Ans 1. Correct option – c: Both force and torque
An electric dipole placed in a non-uniform electric field will experience both force and torque.
Ans 2. Correct option – b: 2/3
Ф = q/Ԑ
= (2q/ Ԑ0)/ (3q/ Ԑ0)
Thus, N1/N2 = 2/3
Ans 3. Correct option – b: IR =IG
From given diagram, we can observe that when switch is closed or open the reading on galvanometer is same and resistance P and R are not same.
Using the balanced condition, we can say that
Current in resistance R and G will be same.
Thus, IR =IG
Ans 4. Correct option – d:
Length of wire 1, L1 = L
Diameter of 1st wire, D1 = 2D
Length of wire 2, L2 = 2L
Diameter of 2nd wire, D2 = 3D
Hence, the ratio of the potential difference of two wires are
Ans 5. Correct option – a:
N1 = 30
A1 = 3.6 × 10-3 m2
B1 =0.25 T
N2 = 42
A2 = 1.8 × 10-3 m2
B2 =0.5 T
Ans 6. Correct option – d: , into the plane of the paper.
Now for the given figure, the magnetic field at centre M due to current flowing through DA will be
Similarly, the magnetic field due to the current flowing through BC is
Whereas, magnetic field due to AB and CD will be zero since point M lies on the straight line.
Hence net magnetic field for the given case will be
And by using the right-hand thumb rule we can conclude that direction of the magnetic field will be in the plane of the paper.
Ans 7. Correct option – d:
a dielectric is introduced into the gap between the plates of the capacitor.
From the given condition, the effective resistance for two circuits is
Based on the preceding equations, we may conclude that increasing the gap between the plates of the capacitor reduces capacitance, which causes R1 to increase, resulting in a decrease in current.
As a result, the brightness of the bulb will diminish because its brightness is directly proportional to the current running through it.
Hence, the bulb will glow brighter when a dielectric is introduced into the gap between the plates of the capacitor.
Ans 8. Correct option – d: 250 V
f = 50 Hz
L = 318 mH = 0.318
R = 75 Ω
VR = 150 V
Current through R,
Hence the total voltage,
Ans 9. Correct option – d:
Electric potential for a dipole is given as
Ans 10. Correct option – b: k
The force between two small spheres is given as
Whereas the force between them in the dielectric medium is
Correct option – d: a gap only
Taking out the infinity plug introduces the air gap in the circuit. Since air is a bad conductor of electricity, no current flows, implying that the infinity resistance in the circuit is introduced.
Ans 12. Correct option – b: 270 J
Voltage, V = 15 V
Time, t =60 s
Internal resistance, r = 50 Ω
Heat energy dissipated in time t is given gas
Ans 13. =Correct option – a: Energy
Lenz’s law is based on the principle of conservation of energy.
Ans 14. Correct option – b: 30°
Ans 15. Correct option – a: 1.2 μT, Vertically upward
Current, I = 15 A
Distance, d = 2.5 m
The magnitude of the magnetic field,
And according to the right-hand thumb rule, the direction magnetic field will be upward.
Ans 16. Correct option – c: 102 V
Inductance, L = 10 H
ΔI = 11 – 2 = 9 A
Time, t = 0.9 sec
Ans 17. Correct option – d:
A charge Q is placed at the centre of the line joining two charges q and q as shown below.
Now, for the system to be in equilibrium force between charges must be zero (ie., F =0).
Ans 18. Correct option – c:
For the given case we know that electric flux is the dot product of the electric field and area of the cross section.
Ans 19. Correct option – d: 2 Ω
Balancing length, l1 = 120 cm
Shunted resistance, R = 1 Ω
New balancing length after shunting, l2= 40 cm
Ans 20. Correct option – d:
The electron will continue to move with the same velocity v along the axis of the solenoid.
As we know when an electron is projected with velocity v along the axis of a current-carrying long solenoid, it will continue to move with the same velocity v along the axis of the solenoid.
It is placed in a space varying magnetic field that does not vary with time.
A metal plate can be heated by any of the flowing methods.
- Passing DC or AC through plates
- Keeping it time-varying magnetic field which produces induced current.
Ans 23. Correct option – d: Zero
Power = VI or EI
Ans 24. Correct option – a: 6×106 m/s
Potential difference, V =100 V
Charge of electron, e = 1.6× 10-19 C
Ans 25. Correct option – c: A stationary charge
As we know charges at rest or rest remain unaffected by magnetic fields since force depends on velocity, and velocity is zero in the case of stationary charges.
Now the force acting on test charge is
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