## Tuesday, 13 June 2017

### WORKSHEET1 CBSE CLASS 12 PHYSICS CHAPTER1 ELECTRIC CHARGE AND FIELD

1.An attractive force of 5N is acting between two charges of 2μc and -2μc placed at some distance. If the charges are mutuall touched and placed again at the same distance, what will be the new force between them. Zero
2. Force of attraction between two charges at a distance d is F. What distance part should they kept in the medium so that force   between them is F/3.                                                                                                         New distance = (3)1/2r
3. Two point charges q1 and q2 are 3 m apart and their combined charge is 20 μc. If one repels the other with a force of 0.075 N,  what are twocharges?                                                                                                     Q 1= 15 μc and Q2 = 5 μc.
4. A charge P repels charge Q but it attracts charge R. If R repels positively charged Body S, then find nature of charge on Q.
Q is negative
5. The force of attraction between two point charges placed at distance d apart in a medium is F. What should be the distance apart in the same medium so that the force of attraction between them becomes F/4?
New distance=2d
6. Two point charges of 2 μC and 6 μC repel each other with a force of 12 N. If each is now given additional charge of -4 μc,  find new force?                                                                                                                F1 = -4 N.
7. The sum of two point charges is 6µc. They attract each other with a force of 0.9 N. When kept 40 cm apart in vacuum. Find their charges.                                                                                                                    q1= 8 X 10 -6 C and q2 = -2 X 10 -6 C
8.Two point charges, q =8×10-8 C and Q= -2×10-8 C are separated by a distance of 10 cm in air. What is the net electric field at the mid- point between the charges.                                                                              Using the formulae=F/Q =3.6x 105
9. Two point charges 4 Q, Q are separated by 1 m in air. At what point on the line joining the charges is the electric field     intensity zero?                                                                                                               x=2/3 m
10 .Two point charges of 16μC and -9μC are placed 8cm apart in air. Determine the position of the point at which resultant   electric field is zero.
11 .Eight identical point charges of q Coulomb each are placed at corners of a cube of each side 0.1m .Calculate electric field at
the center of the cube. Calculate the field at the center when one of the corner charges is removed.
i) zero ii) E = (1.2 x 1012)q N/C
12. If the radius of the Gaussian surface enclosing a charge is halved, how does the electric flux through the Gaussian surface change?                                                                                                                        No change
13. A charge Q micro coulomb is placed at the centre of a cube. What would be the flux through one face?
Q/6ε0
14.The electric field in a certain region of space is (5i+4j-4k) x 105 N/C. Calculate the electric flux due to this field over an area  of (2i-j) x 10-2 m2                                                                                                         ɸ=E.S = 6 x 103 Nm2C-1
15. A sphere of radius 0.03m has a point charge of q = 7.6μC is located at its center. Find the electric flux
through it                                                                                                                      Φ=q/ɛ0 = 8.6 x 105Nm2C-1
16. A point charge of 17.7μC is located at the centre of a cube of side 0.03m. Find the electric flux through each face of the   cube.
1/6φ=1/6q/ɛ0 = 3.3 x 105Nm2C-1
17. 5,000 lines of force enter a certain volume of space and three thousands lines emerged from it. What is the total charge in  Coulomb within the volume?                                                                      -1.77 x 10-8 C
18.  A spherical Gaussian surface encloses a charge of 8.85 x 10-8 C
i. Calculate the electric flux passing through the surface
ii. If the radius of the Gaussian surface is doubled, how would the flux change?
i)104 Nm2C-1 ii) 104 Nm2C-1