Statements at a glance
1. Gravitational force is weaker but dominating than Coulomb force.
2. When two identical spheres carrying unequal +ve charges are brought in contact, charges will be equally distributed and force of repulsion will increase.
3. A ?vely charged rod can attract an uncharged ball and +ve ball.
4. Work done in taking a charge along a closed path is zero.
5. Field lines cannot be inclined to surface.
6. Field lines cannot form closed loops
7. Field lines should be perpendicular to surface.
8. Field due to a point charge varies inversely to r2
9. Field due to dipole varies inversely to r3
10. Electric field is parallel to dipole along axial line and along equatorial line.
11. Electric field is twice along axial line than in equatorial line.
12. Net force is zero on an electric dipole placed in uniform electric field.
13. At the centre of a dipole there is field, but potential is zero.
14. The value of potential at infinite distance from +ve or-ve charge is zero.
15. In midway b/w two equal like charges, electric field is zero, but potential is non zero.
16. Work done in equipotential surface is zero.
17. Stable equilibrium, on dipole in uniform electric field whn torque is zero, ?=0, dipole moment is in the direction of EF.
18. Unstable equilibrium, whn torque is zero, but, ?=180, dipole moment is opposite to EF.
19. Rotating a dipole once completely, wd is zero.
20. From stable equilibrium to unstable equilibrium wd is 2PE.
21. WD is zero
A] Whn a charge moves in a circle with another charge kept at the centre.
B] Whn a charge moves along an ellipse kept a charge at centre.
C] Whn a dipole is rotated once completely in another dipole field.
22. The flux depends only on net charge enclosed by the closed surface, not on position of charges
23. EMF is the difference in potential b/w the terminals of the cells whn circuit is open, potential difference is the difference in potential b/w any points of a circuit whn the circuit is closed.
24. In metals current carriers are electrons.
25. In electrolytes nd in gases current carriers are +vely nd ? vely charged ions.
26. In semi conductors current carriers are +vely nd ?vely charged holes.
27. The current due to random motion of free electrons is zero.
28. Electric current established with speed of light so every point of circuit experiences an electron drift. So current produces instantly.
29. The slope of VI graph gives R.
30. Alloys hav greater resistance than metals.
31. Alloys hav high resistivity nd zero temp. coefficient
32. Semiconductors hav ?ve temp. coefficient
33. Whn a battery is short circuited, then the entire power delivered by the battery is dissipated inside it as heat energy.
34. Whn internal resistance is small, maximum current is drawn from a battery.
35. Whn temp. increases internal resistance decreases.
36. In a battery, high internal resistance is used for safety.
37. Rheostat is used to obtain maximum balancing length by adjusting it.
38. Whn galvanometer shows 0 deflections, no current flow thrgh potentiometer.
39. Increasing length of potentiometer wire, increases its sensitivity bcoz potential gradient is small.
40. Resistance of copper is small, so it is used for potentiometer wire. If it is short circuited no pd will be available.
41. In series 60w glows brighter than 100w. becoz P ? R.
42. In parallel 100w bulb glows brighter than 60w. becoz V kept constant ? 1/R
43. Magnetic field is zero at any point along a straight conductor.
44. +ve charge cannot move along magnetic line of force, since direction of force is perpendicular to both velocity and magnetic field.
45. Lorentz force is perpendicular to velocity so on tangential acceleration and KE remain constant
46. Wd by lorentz force is zero becoz force nd displacement are perpendicular to each other.
47. Path of charged particle:
Parallel to mag.f ? straight line path.
Perpendicular to mag.f ? circular path.
At an angle wid mag.f ? helical.
48.Wd in full rotation for a mag. Dipole in a uniform mag. Field is zero.
49. Mag. field lines are continuous closed loops, but electric field lines are discontinuous.
50. Soft iron is used to make core of transformer, hysterisis loss is minimum for soft iron.
*Wd ? work done
*EF ? electric field
Moderation Team
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