TN 12TH PHYSICS - Online Test

Q1. An excess of silver nitrate is added to 100ml of a 0.01M solution of pentaaqua chloride chromium(III)chloride. The number of moles of AgCl precipitated would be
Answer : Option B
Explaination / Solution:

The complex is [M(H2O)5 Cl] Cl2

1000 ml of 1M solution of the complex gives 2 moles of Cl ions

1000 ml of 0.01M solution of the complex will give

[100 ml x 0.01M x 2Cl-] / [1000 ml x 1M] = 0.002 moles of C  ions


Q2. An ionic compound AxBy crystallizes in fcc type crystal structure with B ions at the centre of each face and A ion occupying entre of the cube. the correct formula of AxBy is
Answer : Option B
Explaination / Solution:

number of A ions = (Nc/8) = (8/8)=1

number of B ions = (Nf/2) = (6/2) =3


Q3. A zero order reaction X →Product , with an initial concentration 0.02M has a half life of 10 min. if one starts with concentration 0.04M, then the half life is
Answer : Option C
Explaination / Solution:




Q4. A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is,
Answer : Option B
Explaination / Solution:

End A of the rod acts as an object for mirror and A' will be its image. By mirror formula, image distance of A is VA.


VA = -15cm

Also image distance of C

Vc= -20 cm

The length of image = | VA-VC |

 = | -15-(20) | = 5cm


Q5. Two point white dots are 1 mm apart on a black paper. They are viewed by eye of pupil diameter 3 mm approximately. The maximum distance at which these dots can be resolved by the eye is, [take wavelength of light, λ = 500 nm]
Answer : Option B
Explaination / Solution:

Resolution limit = 1.22 × λ / D

D - diameter of pupil = 3 mm

λ - wavelength = 500 nm

 Resolution limit = distance between the dots / resolving diameter

= 1mm/d

[ 1.22 × λ ] / D =  1mm / d

D = [1mm × D ] / [ 1.22 × λ ] = [ 1 x 10-3 × 3 x 10-3 ] / [ 1.22 × 500 x10-9 ]

 d = 4.918 ≈ 5m


Q6. Which charge configuration produces a uniform electric field?
Answer : Option C
Explaination / Solution:
No Explaination.


Q7. In an electron microscope, the electrons are accelerated by a voltage of 14 kV. If the voltage is changed to 224 kV, then the de Broglie wavelength associated with the electrons would
Answer : Option C
Explaination / Solution:

deBroglie wavelength λ 1/√V

 λ12 = √(V2/V1) = √(224/14) = √16 = 4

λ1 = 4λ2

λ2 = λ1/4


Q8. A wire of resistance 2 ohms per meter is bent to form a circle of radius 1m. The equivalent resistance between its two diametrically opposite points, A and B as shown in the figure is

Answer : Option B
Explaination / Solution:


Q9. In a hydrogen atom, the electron revolving in the fourth orbit, has angular momentum equal to
Answer : Option D
Explaination / Solution:

Angular momentum L = n h

For n = 4, L = 4h = 4h /2 π =2h/ π 


Q10. An electron moves straight inside a charged parallel plate capacitor of uniform charge density σ. The time taken by the electron to cross the parallel plate capacitor when the plates of the capacitor are kept under constant magnetic field of induction  is

Answer : Option D
Explaination / Solution: