ABC is an equilateral triangle. Charges + q are placed at each corner. The electric intensity at O will be

|
(a) |
(b) |
(c) Zero |
(d) |
ABC is an equilateral triangle. Charges + q are placed at each corner. The electric intensity at O will be

|
(a) |
(b) |
(c) Zero |
(d) |
(c) Zero
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The energy in MeV is released due to transformation of 1 kg mass completely into energy (c = 3
| (a) 7.625 ×10 MeV |
(b) 10.5 |
(c) 2.8 |
(d) 5.625 |
Five balls numbered 1 to 5 are suspended using separate threads. Pairs (1, 2), (2, 4) and (4, 1) show electrostatic attraction, while pair (2, 3) and (4, 5) show repulsion. Therefore ball 1 must be
|
(a) Positively charged |
(b) Negatively charged |
(c) Neutral |
(d) Made of metal |
A magnet of magnetic moment M oscillating freely in earth's horizontal magnetic field makes n oscillations per minute. If the magnetic moment is quadrupled and the earth's field is doubled, the number of oscillations made per minute would be
|
(a) |
(b) |
(c) 2 |
(d) |
Lens used to remove long sightedness (hypermetropia) is
|
(a) Concave lens |
(b) Plano-concave lens |
|
(c) Convexo-concave lens |
(d) Convex lens |
If induction of magnetic field at a point is B and energy density is U then which of the following graphs is correct
|
(a) |
(b) |
(c) |
(d) |
The shortest wavelength in the Lyman series of hydrogen spectrum is 912 Å corresponding to a photon energy of 13.6 eV. The shortest wavelength in the Balmer series is about
| (a) 3648 Å | (b) 8208 Å | (c) 1228 Å | (d) 6566 Å |
A plane mirror produces a magnification of
| (a) -1 | (b) +1 | (c) Zero | (d) Between 0 and +∞ |
In a semiconductor
|
(a) There are no free electrons at any temperature |
|
(b) The number of free electrons is more than that in a conductor |
|
(c) There are no free electrons at 0 K |
|
(d) None of these |
If the distance between a point source and screen is doubled, then intensity of light on the screen will become
|
(a) Four times |
(b) Double |
(c) Half |
(d) One-fourth |