Electric charge and field impoartant question for neet-
1.Which of the following charge cannot be present on oil drop in Millikan’s experiement?
(1) 4.0 x 10-19 C
(2) 6.0x 10-1 C
(3) 10.0 × 10-10 C
(4) all of them
Ans.- 4
2.If in Millikan’s oil drop experiment charges on drops are found to be 8µC, 12µC, 20µC, then quanta of charge is
(1) 8µC
(2) 4µC
(3) 20μC,
(4)12μC
Ans.- 2
3.In nature, the electric charge of any system is always equal to
(1) Half integral multiple of the least amount of charge
(2) Zero
(3) Square of the least amount of charge
(4) Integral multiple of the least amount of charge
Ans.- 4
4.A glass rod rubbed with silk is used to charge a gold leaf electroscope and the leaves are observed to diverge. The electroscope thus charged is exposed to X-rays for a short period. Then
(1) The divergence of leaves will not be affected
(2) The leaves will diverge further
(3) The leaves will collapse
(4) The leaves will melt
Ans.- 2
5.Consider a neutral conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then:
(1) Negative and distributed uniformly over the surface of the sphere
(2) Negative and appears only at the point on the sphere closed to the point charge
(3) Negative and distributed non-uniformly over the entire surface of the sphere
(4) Zero
Ans.- 4
6.If a body has positive charge on it, then it means it has
(1) Gained some protons
(2) Lost some protons
(3)Gained some electrtons
(4) Lost some electrons
Ans.- 4
7.Sure check for presence of electric charge is
(1) Process of induction
(2) Repulsion between bodies
(3) Attraction between bodies
(4) Frictional force between bodies
Ans.- 2
8.If a solid and a hollow conducting sphere have same radius then
(1) Hollow sphere will hold more maximum charge
(2) Solid sphere will hold more maximum charge
(3) Both the spheres will hold same maximum charge
(4) Both the sphere can’t hold charge
Ans.- 3
9.When a conducting soap bubble is negatively charged then
(1) Its size starts varying arbitrarily
(2) Il expands
(3) It contracts
(4) No change in its size takes place
Ans.- 2
10.Five balls marked a to e are suspended using separate threads. Pairs (b, c) and (d, e) show electrostatic repulsion while pairs (a, b), (c, e) and (a, e) show electrostatic attraction. The ball marked a must be
(1) Negatively charged
(2) Positively charged
(3) Uncharged
(4) Any of the above is possible
Ans.- 3
- When a plastic rod rubbed with wool is brought near the knob of a negatively charged gold leaf electroscope, the gold leaves
(1) Contract
(2)Dilate
(3) Start oscillating
(4) Collapse completely
Ans.- 2
- The unit of permittivity of free space e is
(1) coulomb/newton-metre
(2) coulomb/newton-metre
(3) newton-metre/coulomb
(4) coulomb/(newton-metre)
Ans.- 2
13.When the velocity of a relativistic charged particle increases. It’s specific charge
(1)Decreases
(2) Increses
(3) Remains same
(4) First decreases then increases
Ans.- 1
14.Smallest unit of charge is
(1) frankline
(2) faraday
(3) coulomb
(4) e.m.u.
Ans.- 1
- Find the number of electron that should be removed from a coin so that it acquires a charge of 10 coulomb
(1) 6.25 x 1011
(2) 1.6 x 10
(3) 1.6 x 10-
(4) 6.25 x 1012
Ans.- 4
16.Two similar small spheres having +q and -q charge are kept at a certain distance. F force acts between the two. If in the middle of two spheres, another similar small sphere having +q charge is kept, then it will experience a force in magnitude and direction as
(1) zero, having no direction
(2) 8 F, towards + q charge
(3) 8 F, towards – q charge
(4) 4F, towards + q charge
Ans.- 3
17.The force between two charges 0.06 m apart is 5 N. If each charge is moved towards the other by 0.01 m, then the force between them will become
(1) 7.20 N
(2) 11.25 N
(3) 22.50 N
(4) 45.00 N
Ans.- 2
18.Two charged spheres separated at a distance d exert a force F on each other. If they are immersed in a liquid of dielectric constant 2, then what is the force (if all conditions are same)
(1)F/2
(2) F
(3) 2F
(4) 4F
Ans.- 1
- Electric charges of 1µC.-1µC and 2 µC are placed in air at the corners A, B and C respectively of an equilateral triangle ABC having length of each side 10 cm. The resultant force on the charge at C is
(1) 0.9 N
(2) 1.8 N
(3) 2.7 N
(4) 3.6 N
Ans.- 2
20.Two small conducting spheres of equal radius have charges +10 µC and -20 µC respectively and placed at a distance R from each other. They experience force F,. If they are brought in contact and separated to the same distance, they experience force F₂. The ratio of F, to F₂ is
(1) 1:8
(2) 8:1
(3) 1:2
(4) 2:1
Ans.- 2
- Two charges + 4e and +e are at a distance x apart. At what distance, a charge q must be placed from charge +e, so that it is in equilibrium?
(1) x/2
(2) 2x/3
(3) x/3
(4) x/4
Ans.- 3
22.A charge Q is placed at each of the two opposite corners of a square. A charge q is placed at each of the other two corners. If the resultant force on Q is zero, then
(1) Q = √2q
(2) Q-√2q
(3) Q=2√2q
(4) Q=-2√2q
Ans.- 4
- Two point charges + 2 C and + 6 C repel each other with a force of 12 N. If a charge of -4C is given to each of these charges, the force now is
(1) 4 (repulsive)
(2) 4N (attractive)
(3) 12 N (attractive)
(4) 8 N (repulsive)
Ans.- 2
24.Two equal positive charges Q are fixed at points (a, 0) and (-a, 0) on the x-axis. An opposite charge -q at rest is released from point (0, a) on the y- axis. The charge -q will
(1) Move to infinity
(2) Move to origin and rest there
(3) Undergo SHM about the origin
(4) Execute oscillatory periodic motion but not SHM
Ans.- 4
25.Three equal charges are placed on the three comer of a square. If the force between q, and q₂ is F12 and that between q, and q, is F₁3, then the ratio of magnitudes (F12/F13) is
(1) 1/2
(2) 2
(3) 1/√2
(4) √2
Ans.- 2