13

CT1/2022-2023
25018/XII/042/2022-23
SUBJECT – PHYSICS
CYCLE TEST – I
DATE : 18/07/2022

MM : 30 Marks
Time : 50 Minutes

General Instructions :
• There are 12 questions in all. All questions are compulsory.
• This question paper has four sections: Section A, Section B, Section C and Section D.
• Section A contains four questions of one marks each, Section B contains two questions of two marks each,
• Section C contains four questions of three marks. Section D contains 2 questions of 5 marks each.

Section A

1. Four point charges q_a=2µC, q_b=-5µC, q_c=2µC, q_d=-5µC are located at the corners of a square ABCD of side 10 cm what is the force on a charge of 1µC are placed at the centre of the square? (1)

2. Name the physical quantity whose SI unit is voltmeter. Is it a vector or a scalar quantity? (1)

3. Draw the electric field lines due to a point charge Q>0 and Q<0?

4. What does Q₁+Q₂=0 signify?

Section B

5. Is the force acting between two point electric charges Q1 and Q2 kept at some distance apart in air attractive or repulsive when Q1Q2>0. Q1Q2<0. (2)

6. Two charges of magnitude -2Q and +Q are located at points (a,0) and (4a,0) respectively what is the electric flux due to these charges through a sphere of radius 3a with its centre at the origin? (2)

Section C

7. The electrostatic force on a small sphere of charge 0.4µC due to another sphere of charge -0.8 micro coulomb in air is 0.2 Newton?

1. What is the distance between the two spheres?
2. What is the force on the second sphere due to the first? (3)

8. Two point charges 3µC and -3µC are located 20 cm apart in vacuum. Calculate the electric field at the midpoint of the line AB joining the two charges? What is the force experienced by a negative test charge of magnitude 1.5×10^-9 C placed at this point? (3)

9. An electric dipole with moment moment 4×10^-9 C meter is aligned at 30° with the direction of a uniform field of magnitude 5×10⁴ N per coulomb. Calculate the magnitude of the torque acting on the dipole. (3)

10. Consider a uniform electric field is equal to 3×10³ i Newton per coulomb.

1. What is the electric flux of this field through a square of 10 cm on a side whose plane is parallel to the YZ plane?
2. What is the flux through the same square if the normal to its plane makes a 60° angle with the X-axis? (3)

Section D

11. (i) In a medium the force of attraction between two point electric charges distance d apart is equal to F. What distance apart should these be kept in the same medium so that the force between them becomes (i) 3F (ii) F/3.
(ii) Using Gauss’stheorem show mathematically that for any point outside the shell the field due to a uniformly charged thin spherical shell is the same as if the entire charge of the shell is concentrated at the centre. Why do you expect the electric field inside the shell to be zero according to this theorem?

12. A potential difference is set up between the plates of a parallel plate capacitor by a battery and then the battery is removed if the distance between the plates is increased then how the
(i) charge (ii) potential difference (iii) electric field (iv) energy (v) energy density will change?