Important Questions of Electric Charges and Fields Physics | Zigya

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31.

If the electric flux entering and leaving a closed surface are 6 x 106 and 9 x 106 SI units respectively, then the charge inside the surface of permittivity of free space ε0 is

  • ε0 × 106

  • − ε0 × 106

  • − 2ε× 106

  • 0 × 106


32.

Two identical thin rings, each of radius 10 cm carrying charges 10 C and 5 C are coaxially placed at a distance 10 cm apart. The work done in moving a charge q from the centre of the first ring to that of the second is

  • q8πε0 2 + 12

  • q8πε0 2 -1 2

  • q8πε0 2 + 12

  • q4πε0 2 - 12


33.

Choose the correct statement

  • Polar molecules have permanent electric dipole moment

  • CO2  molecule is a polar molecule 

  • H2O  is a non-polar molecule

  • The dipole field at large distances falls of as 1r2


34.

The electric field between two infinitely charged plates with air medium in between, in terms of the surface charge density σ is

  • 4πε0

  • σ4πε0

  • σε0

  • 4πσε0


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35.

Electric charge is uniformly distributed along a long straight wire of radius 1 mm. The charge per cm length of the wire is Q coulomb. Another cylindrical surface of radius 50 cm and length 1 m symmetrically encloses the wire. The total electric flux passing through the cylindrical surface is

  • Qε0

  • 100 Qε0

  • 10 Qπε0

  • 100 Qπε0


36.

A charged particle q is shot towards another charged particle Q which is fixed, with a speed v. It approaches Q upto a closest distance r and then returns. If q is shot with speed 2v, the closest approach would be

  • r4

  • r2

  • 2r

  • r


37.

A dipole of electric dipole moment p is placed in a uniform electric field of strength E. If θ is the angle between positive directions of p and E, then the potential energy of the electric dipole is largest when θ is

  • π4

  • π2

  • π

  • zero


38.

Two conducting spheres of radii 3 cm and 1 cm are separated by a. distance of 10 cm in free space. If the spheres are charged to same potential of 10 V each, the force of repulsion between them is

  • 13 × 10-9 N

  • 29 × 10-9 N

  • 19 × 10-9 N

  • 49 × 10-9 N


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39.

If q1 + q2 = q, then the value of the ratio q1q, for which the force between q1 and q2 is maximum is

  • 0.25

  • 0.75

  • 1

  • 0.5


40.

Two charged spherical conductors of radii R1 and R2 are connected by a wire. Then the ratio of surface charge densities of the spheres σ1/σ2 is

  • R1 / R2

  • R2 / R1

  • R1 / R2

  • R12 / R22


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