MCQ
The potential difference between the two plates of a parallel plate capacitor is constant. When air between the plates is replaced by dielectric material, the electric field intensity:
- ADecreases
- BRemains unchanged
- CBecomes zero
- DIncreases
✓
Answer
- Decreases
Explanation:
In general capacitance of parallel plate capacitor is given by:
$\text{C}=\frac{\text{K}\in_0\text{A}}{\text{d}}$
Where C is capacitance, k is relative permittivity of dielectric material, ϵ0 is permittivity of free space constant, A is area of plates and d is distance between them. Therefore, the capacitance of parallel plates is increased by the insertion of a dielectric material. Further, the capacitance is inversely proportional to the electric field between the plates, and hence the presence of the dielectric decreases the effective electric field.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A student says that he had applied a force $\text{F}=-\text{k}\sqrt{\text{x}}$ on a particle and the particle moved in simple harmonic motion. He refuses to tell whether k is a constant or not. Assume that he was worked only with positive x and no other force acted on the particle.
→- As x increases k increases.
- As x increases k decreases.
- As x increases k remains constant.
- The motion cannot be simple harmonic.
A silver and a copper voltmeters are connected in parallel across a 6 volt battery of negligible resistance. In half an hour, 1 gm of copper and 2 gm of silver are deposited. The rate at which energy is supplied by the battery will approximately be (Given E.C.E. of copper = 3.294 
and E.C.E. of silver = 1.118 
|
(a) 64 W |
(b) 32 W |
(c) 96 W |
(d) 16 W |
In a working nuclear reactor, Cadmium rods, (control rods) are used to
|
(a) Speed up neutrons |
(b) Slow down neutrons |
|
(c) Absorb some neutrons |
(d) Absorb all neutrons |
Let Q and W denote the amount of heat given to an ideal gas and the work done by it in an isothermal process.
- Q = 0
- W = 0
- Q ≠ W
- Q = W
Two thin lenses, one of focal length + 60 cm and the other of focal length – 20 cm are put in contact. The combined focal length is
|
(a) + 15 cm |
(b) – 15 cm |
(c) + 30 cm |
(d) –30 cm |
The force between the plates of a parallel plate capacitor of capacitance C and distance of separation of the plates d with a potential difference V between the plates, is
|
(a) |
(b) |
(c) |
(d) |
A person travelling on a straight line moves with a uniform velocity v1 for a distance x and with a uniform velocity v2 for the next equal distance. The average velocity v is given by:
→-
$\text{v}=\frac{\text{v}_1+\text{v}_2}{2}$
-
$\text{v}=\sqrt{\text{v}_1\text{v}_2}$
-
$\frac{2}{\text{v}}=\frac{1}{\text{v}_1}+\frac{1}{\text{v}_2}$
-
$\frac{1}{\text{v}}=\frac{1}{\text{v}_1}+\frac{1}{\text{v}_2}$
The capacity of a condenser in which a dielectric of dielectric constant 5 has been used, is C. If the dielectric is replaced by another with dielectric constant 20, the capacity will become
|
(a) |
(b) 4C |
(c) |
(d) 2C |
For a short magnet with magnetic dipole moment $\vec{m}$, its magnetic field at distance $d$ from its centre on its equator is __________ .
→Activity of radioactive element decreased to one third of original activity 
in 9 years. After further 9 years, its activity will be
|
(a)
|
(b) 
|
(c) |
(d) |
