- AInsulators.
- BConductors.
- CSemiconductors.
- DSuperconductors.
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$10\text{cm}$
$10\sqrt{2}\text{cm}$
$\frac{10}{\sqrt{2}}\text{cm}$
A uniform wire is bent in the form of a circle of radius R. A current I enters at A and leaves at C as shown in the figure :
If the length ABC is half of the length ADC, the magnetic field at the centre O will be

|
(a) Zero |
(b) |
(c) |
(d) |
The largest distance between the interatomic planes of a crystal is 10-7cm. The upper limit for the wavelength of X-rays which can be usefully studied with this crystal is
| (a) 1 Å | (b) 2 Å | (c) 10 Å | (d) 20 Å |
Assuming that the dimmest visible star to the naked eye has a magnitude of about 6. Brightness of planet Venus (magnitude = – 4) w.r.t. this star is
|
(a) 10,000 times brighter |
(b) 2000 times brighter |
|
(c) 15000 times brighter |
(d) 4000 times brighter |
Dual nature of radiation is shown by
|
(a) Diffraction and reflection |
(b) Refraction and diffraction |
|
(c) Photoelectric effect alone |
(d) Photoelectric effect and diffraction |
The current in a LR circuit builds up to
th of its steady state value in 4s. The time constant of this circuit is
|
(a) |
(b) |
(c) |
(d) |