Physics Term 1 2021-2022 Science (English Medium) Class 12 Question Paper Solution

A negatively charged object X is repelled by another charged object Y. However an object Z is attracted to object Y. Which of the following is the most possibility for the object Z?

positively charged only

negatively charged only

neutral or positively charged

neutral or negatively charged

In an experiment three microscopic latex spheres are spread into a chamber and became charged with charges +3e, +5e and −3e respectively. All the three spheres came in contact simultaneously for a moment and got separated. Which one of the following are possible values for the final charge on the spheres?

+5e, −4e, +5e

+6e, +6e, −7e

−4e, +3.5e, +5.5e

+5e, −8e, +7e

An object has charge of 1 C and gains 5.0 × 10¹⁸ electrons. The net charge on the object becomes ______.

−0.80 C

+0.80 C

+1.80 C

+0.20 C

Kirchoffs first rule ∑I = 0 and second rule ∑IR = ∑E (where the symbols have their usual meanings) are respectively based on ______.

conservation of momentum and conservation of charge

conservation of energy, conservation of charge

conservation of charge, conservation of momentum

conservation of charge, conservation of energy

The electric power consumed by a 220 V − 100 W bulb when operated at 110 V is ______.

25 W

30 W

35 W

45 W

Which of the following has negative temperature coefficient of resistivity?

metal

metal and semiconductor

semiconductor

metal and alloy

Two wires carrying currents I₁ and I₂ lie, one slightly above the other, in a horizontal plane as shown in figure. The region of vertically upward strongest magnetic field is ______.

I

II

III

IV

Two parallel conductors carrying current of 4.0 A and 10.0 A are placed 2.5 cm apart in vacuum. The force per unit length between them is ______.

6.4 × 10⁻⁵ N/m

6.4 × 10⁻² N/m

4.6 × 10⁻⁴ N/m

3.2 × 10⁻⁴ N/m

If an ammeter is to be used in place of a voltmeter, then we must connect with the ammeter a ______.

low resistance in parallel

low resistance in series

high resistance in parallel

high resistance in series

The magnetic field at the centre of a current carrying circular loop of radius R, is B₁. The magnetic field at a point on its axis at a distance R from the center of the loop is B₂. Then the ratio (B₁/B₂) is ______.

`2sqrt 2`

`1/sqrt 2`

`sqrt 2`

2

The self-inductance of a solenoid of 600 turns is 108 mH. The self-inductance of a coil having 500 turns with the same length, the same radius and the same medium will be ______.

95 mH

90 mH

85 mH

75 mH

The rms current in a circuit connected to 50 Hz ac source is 15 A. The value of the current in the circuit `(1/600)s` after the instant the current is zero, is ______.

`15/sqrt2`A

`15 sqrt 2`A

`sqrt 2/15`A

8 A

In a circuit the phase difference between the alternating current and the source voltage is `pi/2`. Which of the following cannot be the element(s) of the circuit?

only C

only L

L and R

L or C

The electric potential V at any point (x, y, z) is given by V = 3x² where x is in metres and V in volts. The electric field at the point (1 m, 0, 2 m) is ______.

6 V/m along −x-axis

6 V/m along +x-axis

1.5 V/m along −x-axis

1.5 V/m along +x-axis

Which of the diagrams correctly represents the electric field between two charged plates if a neutral conductor is placed in between the plates?

A variable capacitor is connected to a 200 V battery. If its capacitance is changed from 2 µF to X µF, the decrease in energy of the capacitor is 2.0 × 10⁻² J. Calculate the value of X.

1 µF

2 µF

3 µF

4 µF

A potential difference of 200 V is maintained across a conductor of resistance 100 Ω. The number of electrons passing through it in 1 s is ______.

1.25 × 10¹⁹ 

2.5 × 10¹⁸

1.25 × 10¹⁸

2.5 × 10¹⁶

The impedance of a series LCR circuit is ______.

R + X_L + X_C

`sqrt(1/X_C^2 + 1/X_L^2 + R^2)`

`sqrt(X_L^3 - X_C^2 + R^2)`

`sqrt(R^2 + (X_L - X_C)^2)`

When an alternating voltage E = E₀ sin ωt is applied to a circuit, a current `I = I_0 sin(omegat + pi/2)` flows through it The average power dissipated in the circuit is ______.

E_rms . I_rms

E₀I₀

`(E_0I_0)/sqrt2`

Zero

A current carrying wire kept in a uniform magnetic field, will experience a maximum force when it is ______.

perpendicular to the magnetic field

parallel to the magnetic field

at an angle of 45° to the magnetic field

at an angle of 60° to the magnetic field

The voltage across a resistor, an inductor, and a capacitor connected in series to an ac source are 20 V, 15 V and 30 V respectively. The resultant voltage in the circuit is ______.

5 V

20 V

25 V

65 V

In a dc circuit the direction of current inside the battery and outside the battery respectively are ______.

positive to negative terminal and negative to positive terminal

positive to negative terminal and positive to negative terminal

negative to positive terminal and positive to negative terminal

negative to positive terminal and negative to positive terminal

The magnitude of electric field due to a point charge 2q, at distance r is E. Then the magnitude of electric field due to a uniformly charged thin spherical shell of radius R with total charge q at a distance `r/2` (r >> R) will be ______.

`E/4`

0

2E

4E

The horizontal component of earth's magnetic field at a place is 0.2 G whereas it's total magnetic field is 0.4 G. The angle of dip at the place is ______.

30°

45°

60°

90°

The current in the primary coil of a pair of coils changes from 7 A to 3 A in 0.4 s. The mutual inductance between the two coils is 0.5. The induced emf in the secondary coil is ______.

50 V

75 V

100 V

220 V

A square sheet of side 'a' is lying parallel to XY plane at z = a. The electric field in the region is `vec E = cz^2 hat k`. The electric flux through the sheet is ______.

a⁴c

`1/3 a^4c`

`1/3 a^4c`

0

Three charges q, −q and q₀ are placed as shown in figure. The magnitude of the net force on the charge q₀ at point O is `[k = 1/((4 pi epsilon_0))]`

0

`(2kqq_0)/a^2`

`(sqrt 2 kqq_0)/a^2`

`1/sqrt 2 (kqq_0)/a^2`

A + 3.0 nC charge Q is initially at rest at a distance of r₁ = 10 cm from a +5.0 nC charge q fixed at the origin. The charge Q is moved away from q to a new position at r₂ = 15 cm. In this process work done by the field is ______.

1.29 × 10⁻⁵ J

3.6 × 10⁵ J

−4.5 × 10⁻⁷ J

4.5 × 10⁻⁷ J

A car battery is charged by a 12 V supply, and energy stored in it is 7.20 × 10⁵ J. The charge passed through the battery is ______.

6.0 × 10⁴ C

5.8 × 10³ J

8.64 × 10⁶ J

1.6 × 10⁵ C

A straight conducting rod of length l and mass m is suspended in a horizontal plane by a pair of flexible strings in a magnetic field of magnitude B. To remove the tension in the supporting strings, the magnitude of the current in the wire is ______.

`(mgB)/l`

`(mgl)/B`

`(mg)/(lB)`

`(lB)/(mg)`

A constant current is flowing through a solenoid. An iron rod is inserted in the solenoid along its axis. Which of the following quantities will not increase?

The magnetic field at the centre

The magnetic flux linked with the solenoid

The rate of heating

The self-inductance of the solenoid

A circuit is connected to an ac source of variable frequency. As the frequency of the source is increased, the current first increases and then decreases. Which of the following combinations of elements is likely to comprise the circuit?

L, C and R

L and C

L and R

R and C

If n, e, τ and m have their usual meanings, then the resistance of a wire of length l and cross-sectional area A is given by ______.

`("ne"^2A)/(2mtaul)`

`(ml)/("ne"^2tauA)`

`(mtauA)/("ne"^2l`

`("ne"^2tauA)/(2ml)`

A proton and an alpha particle move in circular orbits in a uniform magnetic field. Their speeds are in the ratio of 9 : 4. The ratio of radii of their circular orbits `(r_p/r_alpha)` is ______.

`3/4`

`4/3`

`8/9`

`9/8`

A coil of area 100 cm² is kept at an angle of 30° with a magnetic field of 10⁻¹ T. The magnetic field is reduced to zero in 10⁻⁴ s. The induced emf in the coil is ______.

`5sqrt3  V` 

`50 sqrt3  V` 

5.0 V

50.0 V

A 15 Ω resistor, an 80 mH inductor and a capacitor of capacitance C are connected in series with a 50 Hz ac source. If the source voltage and current in the circuit are in phase, then the value of capacitance is ______

100 μF

127 μF

142 μF

160 μF

Four objects W, X, Y and Z, each with charge +q are held fixed at four points of a square of side d as shown in the figure. Objects X and Z are on the midpoints of the sides of the square. The electrostatic force exerted by object W on object X is F. Then the magnitude of the force exerted by object W on Z is ______.

`F/7`

`F/5`

`F/3`

`F/2`

Two sources of equal emf are connected in series. This combination is, in turn connected to an external resistance R. The internal resistance of two sources are r₁ and r₂ (r₂  > r₁). If the potential difference across the source of internal resistance r₂ is zero, then R equals to:

`(r_1 + r_2)/(r_2 - r_1)`

r₂ − r₁

`(r_1r_2)/(r_2 - r_1)`

`(r_1 + r_2)/(r_1r_2)`

Which of the following statements is correct?

Magnetic field lines do not form closed loops.

Magnetic field lines start from north pole and end at south pole of a magnet.

The tangent at a point on a magnetic field line represents the direction of the magnetic field at that point.

Two magnetic field lines may intersect each other.

The equivalent resistance between A and B of the network shown in figure is ______.

3R Ω

`(3/2)`R Ω

2R Ω

`(2/3)`R Ω

A bar magnet has magnetic dipole moment `barM`. Its initial position is parallel to the direction of uniform magnetic field `barB`. In this position, the magnitudes of torque and force acting on it respectively are ______.

0 and MB

MB and MB

0 and 0

`|barM xx barB|` and 0

Two charges 14 µC and −4 µC are placed at (−12 cm, 0, 0) and (12 cm, 0, 0) in an external electric field `E = (B/r^2)`, where B = 1.2 × 10⁶ N/(cm²) and r is in metres. The electrostatic potential energy of the configuration is ______.

97.9 J

102.1 J

2.1 J

−97.9 J

A 300 Ω resistor and a capacitor of `(25/pi)`µF are connected in series to a 200 V − 50 Hz ac source. The current in the circuit is ______.

0.1 A

0.4 A

0.6 A

0.8 A

The core of a transformer is laminated to reduce the effect of ______.

flux leakage

copper loss

hysteresis loss

eddy current

Assertion (A): A negative charge in an electric field moves along the direction of the electric field.

Reason (R): On a negative charge a force acts in the direction of the electric field.

Both (A) and (R) are true, and (R) is correct explanation of (A).

Both (A) and (R) are true, and (R) is not correct explanation of (A).

(A) is true, but (R) is false.

(A) is false and (R) is also false.

Assertion (A): The poles of a bar magnet cannot be separated.

Reason (R): Magnetic monopoles do not exist.

Both (A) and (R) are true, and (R) is correct explanation of (A).

Both (A) and (R) are true, and (R) is not correct explanation of (A).

(A) is true, but (R) is false.

(A) is false and (R) is also false.

Assertion (A): When radius of a current carrying loop is doubled, its magnetic moment becomes four times.

Reason (R): The magnetic moment of a current carrying loop is directly proportional to the area of the loop.

Both (A) and (R) are true, and (R) is correct explanation of (A).

Both (A) and (R) are true, and (R) is not correct explanation of (A).

(A) is true, but (R) is false.

(A) is false and (R) is also false.

Assertion (A): Higher the range, lower is the resistance of an ammeter.

Reason (R): To increase the range of an ammeter additional shunt is added in series to it.

Both (A) and (R) are true, and (R) is correct explanation of (A).

Both (A) and (R) are true, and (R) is not correct explanation of (A).

(A) is true, but (R) is false.

(A) is false and (R) is also false.

Assertion (A): A step-up transformer cannot be used as a step-down transformer.

Reason (R): A transformer works only in one direction.

Both (A) and (R) are true, and (R) is correct explanation of (A).

Both (A) and (R) are true, and (R) is not correct explanation of (A).

(A) is true, but (R) is false.

(A) is false and (R) is also false.

Equipotentials at a large distance from a collection of charges whose total sum is not zero are ______.

spheres

planes

ellipsoids

paraboloids

Four charges −q, −q, +q and +q are placed at the corners of a square of side 2 L is shown in figure. The electric potential at point A midway between the two charges +q and +q is:

`1/(4 pi epsilon_0) (2q)/L(1 - 1/sqrt5)`

`1/(4 pi epsilon_0) (2q)/L(1 + 1/sqrt5)`

`1/(4 pi epsilon_0) q/(2L)(1 - 1/sqrt5)`

zero

An experiment was set up with the circuit diagram shown in figure.

Given that R₁ = 10 Ω, R₂ = R₃ = 5 Ω, r = 0 Ω and E = 5 V.

The points with the same potential are ______.

b, c, d

f, h, j

d, e, f

a, b, j

An experiment was set up with the circuit diagram shown in figure.

Given that R₁ = 10 Ω, R₂ = R₃ = 5 Ω, r = 0 Ω and E = 5 V.

The current through branch bg is ______.

1 A

`1/3 A`

`1/2 A`

`2/3 A`

An experiment was set up with the circuit diagram shown in figure.

Given that R₁ = 10 Ω, R₂ = R₃ = 5 Ω, r = 0 Ω and E = 5 V.

The power dissipated in R₁ is ______.

2 W

2.5 W

3 W

4.5 W

An experiment was set up with the circuit diagram shown in figure.

Given that R₁ = 10 Ω, R₂ = R₃ = 5 Ω, r = 0 Ω and E = 5 V.

The potential difference across R₃ is ______.

1.5 V

2 V

2.5 V

3 V