## Class/Course - Class XII

### Subject - Physics

#### Total Number of Question/s - 5154

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• 1. Electric Charges and Fields - Quiz

1. A positive point charge 50μC is located in the plane xy at a point with radius vector $\vec{r}_{0}$ = $2\hat{i} + 3\hat{j}$. The electric field $\vec{E}$ at a point with radius vector $\vec{r}$ = $8\hat{i} - 5\hat{j}$, where r0 and r are expressed in meter, is
a) $\left (1.4\hat{i} - 2.6\hat{j}\right )kNC^{-1}$
b) $\left (1.4\hat{i} + 2.6\hat{j}\right )kNC^{-1}$
c) $\left (2.7\hat{i} - 3.6\hat{j}\right )kNC^{-1}$
d) $\left (2.7\hat{i} + 3.6\hat{j}\right )kNC^{-1}$

2. Four point + ve charges of same magnitude (Q) are placed at four corner of a rigid square frame as shown in figure. The plane of the frame is perpendicular to Z axis. If a-ve point charge is placed at a distance z away from the above frame (z< a) -ve charge oscillates along the Z axis
b) It moves away from the frame.
c) It moves slowly towards the frame and stays in the plane of the frame.
d) It passes through the frame only once.

• 2. Electrostatic Potential and Capacitance - Quiz

1. Capacitance of a parallel plate capacitors is 4/3 times its original value, if a dielectric slab of thickness t = d/2 is inserted between the plates ]. The dielectric constant of the slab is
a) 2
b) 6
c) 4
d) 8

2. A capacitor of capacitance C0 is charged to a potential V0 and then isolated. A small capacitor C is then charged from C0, discharged and charged again; the process being repeated n times. Due to this, the potential of the larger capacitor is decreased to V. The value of C is
a) $C_{0}\left (\frac{V_{0}}{V} \right )^{1/n}$
b) $C_{0}\left [\left (\frac{V_{0}}{V} \right )^{1/n} - 1 \right ]$
c) $C_{0}\left [\left (\frac{V_{0}}{V} \right ) - 1 \right ]^{n}$
d) $C_{0}\left [\left (\frac{V_{0}}{V} \right )^{n} + 1 \right ]$

• 3. Current Electricity - Quiz

1. In cells each of emf E and internal resistance r send the same current through an external resistance R whether the cells are connected in series or in parallel. The
a) R = nr
b) R = r
c) r = n R
d) R = √nr

2. Sixteen resistors, rach of resistance 16Ω , are connected in the circuit as shown in figure. The net resistance between A and B is a) 1Ω
b) 2ωΩ
c) 3Ω
d) Ω

• 4. Moving Charges and Magnetism - Quiz

1. Consider six wires coming into or out of the page, all with the same current. Rank the line integral of the magnetic field (from most positive to most negative) taken counter-clockwise around each loop shown. a) B > C > D > A
b) B > C = D > A
c) B > A > C = D
d) C > B = D > A

2. A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. If electric field is switched off, and the same magnetic field is maintained, the electrons move
a) In a circular orbit
b) Along a parabolic path
c) Along a straight line
d) In an elliptical orbit

• 5. Magnetism and Matter - Quiz

1. Which of the following units denotes the dimensions ML2/Q2, where Q denotes the electric charge?
a) Weber (Wb)
b) Wb/m2
c) Henry (H)
d) H/m

2. Two short bar magnets of magnetic moments M each are arranged at the opposite corners of a square of sid d such that their centers coincide with the corners and their axes are parralel. If the like poles are in the same direction, the magnetic induction at any other corner of the square is
a) μ0/4π M/d3
b) μ0/4π 2M/d3
c) μ0/4π M/2d3
d) μ0/4π M3/d3

• 6. Electromagnetic Induction - Quiz

1. Two coils of self inductance L1 and L2 are placed so close together that effective flux in one coil is completely linked with other. If M is mutual inductance between them, then M =
a) L1L2
b) L1/L2
c) (L1L2)2
d) (√L1L2)

2. As a result of change in the magnetic flux linked to the closed loop shown in the figure, an emf V volt is induced in the loop. The work done (joule) in taking a charge Q coulomb once along the loop is a) QV
b) Zero
c) 2QV
d) QV/2

• 7. Alternating Current - Quiz

1. In an a.c. circuit the e.m.f.(e) and the current (i) at any instant are given respectively by
e - E0 sin ωt
The average power in the circuit over one cycle of a.c. is
a) E0I0
b) E0I0/2
c) (E0I0)sinφ
d) (E0I0/2)cosφ

2. A 50 W, 100 V lamp is to be connecteed to an ac mains of 200 V, 500 Hz. What capacitor is essential to be put in series with the lamp?
a) $\frac{25}{\sqrt{2}}\mu F$
b) $\frac{50}{\pi \sqrt{3}}\mu F$
c) $\frac{50}{\sqrt{2}}\mu F$
d) $\frac{100}{\pi \sqrt{3}}\mu F$

• 8. Electromagnetic Waves - Quiz

1. A step-up transformer operates on a 230V line and supplies current of 2A to a loaf. The ratio of the primary and secondary windings is 1:25. The current in the primary coil is
a) 15 A
b) 50 A
c) 25 A
d) 12.5 A

2. Which of the following radiations has the least wavelength?
a) X - rays
b) Y - rays
c) β - rays
d) α - rays

• 9. Ray Optics and Optical Instruments - Quiz

1. A convex lens A of focal length 20cm and a concave lens G of focal length 5 cm are kept along the same axis with the distance d between them. If a parallel beam of light falling on A leaves B as a parallel beam, then distance d is cm will be
a) 25
b) 15
c) 30
d) 50

2. The time taken by light to pass through 4 mm thick glass slab of refractive index 1.5 will be (velocity of light in air = 3 x 108 m/s)
a) 8 x 10-11 s
b) 2 x 10-11 s
c) 8 x 10-8 s
d) 2 x 10-8 s

• 10. Wave Optics - Quiz

1. In young s double- slit experiment , the y-coordinates of central maxima and 10th maxima are 2 cm and 5 cm, respectively . When the YDSE apparatus is immersed in a liquid of refractive index 1.5 , the corresponding y-co-ordinates will be
a) 2 cm, 7.5 cm
b) 3 cm, 6 cm
c) 2 cm, 4 cm
d) 4/3 cm, 103 cm

2. In young double slit experiment, the fringe width is β. If the entire arrangement is placed in a liquid of refractive index n, the fringe width becomes
a) β/n-1
b) β/n
c) nβ
d) β/n+1

• 11. Dual Nature of Radiation and Matter - Quiz

1. The work function of a substance is 4.0 e V. The longest wavelength of light that can cause photoelectron emission from this substance is approximately
a) 540 nm
b) 400 nm
c) 310 nm
d) 220 nm

2. The minimum orbital angular momentum of the electron in a hydrogen atom is
a) h
b) h/e
c) h/2π
d) h/λ

• 12. Nuclei - Quiz

1. The half-life of radium is 1500 years. In how many years will 1g of pure radium be reduced to one centigram?
a) 3.927 x 102 years
b) 9.972 x 102 years
c) 99.927 x 102 years
d) 0.927 x 102

2. A radioactive sample S1 having an activity is μCi has twice the number of nuclei as another sample S2 which has an acitivity of 10μCi. The half lives of S1 and S2 can be
a) 20 years and 5 years, respectively
b) 20 years and 10 years, respectively
c) 10 years each
d) 5 years each

• 13. Semiconductor Electronics: Materials, Devices and Simple Circuit - Quiz

1. A semiconductor is formed by
a) Covalent bonds
b) Electrovalent bonds
c) Coordinate bonds
d) Metallic bonds

2. The given truth table is for which logic gate? a) NAND
b) XOR
c) NOR
d) OR

• 14. Communication Systems - Quiz

1. In which frequencies range space waves are normally propagated
a) HF
b) VHF
c) UHF
d) SHF

a) Omnidirectional type
b) Vertical type
c) Horizontal type
d) None of the above

• 15. Atoms - Quiz

1. When a hydrogen atom is raised from the ground state to fifth state :
a) both KE and PE increases
b) both KE and PE decrease
c) PE increases and KE decreases
d) PE decreases and KE increases

2. The recoil speed of hydrogen atom after it emits a photon in going from n = 2 state n = 1 state is nearly. [Take R = 1.1 x 107 m-1 and and h = 6.63 x 10-34 Js]
a) 1.5 ms-1
b) 3.3 ms-1
c) 4.5 ms-1
d) 6.6 ms-1

• 16. Electric flux and Gauss Law - Quiz

1. A hollow metallic sphere of radius 10cm is given a charge of 3.2 × 10-9C. The electric intensity at a point 4cm from the center is
a) 9 × 10-9 NC-1
b) 299 NC-1
c) 2.88 NC-1
d) zero

2. The electric flux from a cube of edge l is φ. If an edge of the cube is made 2l and the charge enclosed is halved, its value will be
a) 4φ
b) 2φ
c) φ/2
d) φ

• 17. Electrical Measuring Instrument - Quiz

1. An ideal ammeter (zero resistance) and an ideal voltmeter (infinite resistance) are connected as shown in figure. The ammeter and the voltmeter readings are a) 6.25A, 3.75V
b) 3.00A, 5V
c) 3.00A, 3.75V
d) 6.00A, 6.25V

2. Sensitivity of a potentiometer can be increased by
a) increasing the emf of the cell
b) increasing the length of the potentiometer
c) decreasing the length of the potentiometer
d) none of the above

• 18. Heating Effect of Current - Quiz

1. The operating  temperature of the filament of lamp is 20000C. The temperature cofficient of the material of the filament is 0.0050C-1. If the atmospheric temperature is 00C, then the current in the 100W - 200V lamp when it is switched on is nearest to
a) 2.5 A
b) 3.5 A
c) 4.5 A
d) 5.5 A

2. A given resistor cannot carry currents exceeding 20A, without exceeding its maximum power dissipation ratings. By forced air cooling suppose that we increase the rate at which heat can be carried by a factor of 2. Now the maximum current that the resistor can carry is
a) 10A
b) 20$\sqrt{2}$A
c) 30$\sqrt{2}$A
d) 40A