Electric Charges and Fields — Physics STD 12 Science — Question

Assertion  :   A parallel plate capacitor is connected across battery through a key. A dielectric slab of constant K is introduced between the plates. The energy which is stored becomes K times.
Reason     : The surface density of charge on the plate remains constant or unchanged.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true(a) Its kinetic energy increases and its potential and total energies decrease(b) Its kinetic energy decreases, potential energy increases and its total energy remains the same(c) Its kinetic and total energies decrease and its potential energy increases(d) Its kinetic, potential and total energies decreases

An ammeter with internal resistance 90 Ω reads 1.85 A when connected in a circuit containing a battery and two resistors 700 Ω and  410 Ω  in series. Actual current will be(a) 1.85 A(b) Greater than 1.85 A(c) Less than 1.85 A(d) None of these

A proton and an electron are placed in a uniform electric field.

The dielectric constant K of an insulator will be-

Condenser A has a capacity of 15μF when it is filled with a medium of dielectric constant 15. Another condenser  B has a capacity of  1 μF with air between the plates. Both are charged separately by a battery of 100 V. After charging, both are connected in parallel without the battery and the dielectric medium being removed. The common potential now is         (a) 400 V  (b) 800 V(c) 1200 V(d) 1600 V

Wave nature of light is verified by(a) Interference(b) Photoelectric effect(c) Reflection(d) Refraction

Half life of a radio-active substance is 20 minutes. The time between 20% and 80% decay will be(a) 20 minutes(b) 40 minutes(c) 30 minutes(d) 25 minutes

The maximum kinetic energy of the photoelectrons emitted from a surface is dependent on the:

The energy stored in a 50 mH inductor carrying a current of 4 A will be(a) 0.4 J(b) 4.0 J(c) 0.8 J(d) 0.04 J