A parallel plate capacitor has a capacity C. The separation between the plates is doubled and a dielectric medium is introduced between the plates. If the capacity now becomes 2C, the dielectric constant of the medium is
|
(a) 2 |
(b) 1 |
(c) 4 |
(d) 8 |
(c) 4
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Two charges 
and 
are placed in vacuum at a distance d and the force acting between them is F. If a medium of dielectric constant 4 is introduced around them, the force now will be
|
(a) 4F |
(b) 2F |
(c) |
(d) |
Identify the paramagnetic substance
|
(a) Iron |
(b) Aluminium |
(c) Nickel |
(d) Hydrogen |
X-rays of wavelength 0.1 Å allowed to fall on a metal get scattered. The wavelength of scattered radiation is 0.111 Å. If h = 6.624 × 10–34 J-s and m0 = 9 × 10–31 kg, then the direction of the scattered photons will be
| (a) cos–1 (0.547) | (b) cos–1 (0.4484) | (c) cos–1 (0.5) | (d) cos–1 (0.3) |
Assertion : We can measure the potential barrier of a PN junction by putting a sensitive voltmeter across its terminals.
Reason : The current through the PN junction is not same in forward and reversed bias.
|
(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 assertion is false but reason is true. |
The magnetic field at a distance r from a long wire carrying current i is 0.4 Tesla. The magnetic field at a distance 2r is
|
(a) 0.2 Tesla |
(b) 0.8 Tesla |
(c) 0.1 Tesla |
(d) 1.6 Tesla |
A photon of energy 3.4 eV is incident on a metal having work function 2 eV. The maximum K.E. of photo-electrons is equal to
|
(a) 1.4 eV |
(b) 1.7 eV |
(c) 5.4 eV |
(d) 6.8 eV |
