In a full wave rectifiers, input ac current has a frequency ‘n’. The output frequency of current is
|
(a) n/2 |
(b) n |
(c) 2n |
(d) None of these |
(c) 2n
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A hydrogen atom in its ground state absorbs 10.2 eV of energy. The orbital angular momentum is increased by
|
(a) 1.05 |
(b) 3.16 |
(c) 2.11 |
(d) 4.22 |
The material of permanent magnet has
| (a) High retentivity, low coercivity | (b) Low retentivity, high coercivity |
| (c) Low retentivity, low coercivity | (d) High retentivity, high coercivity |
Assertion : X-rays are used for studying the structure of crystals.
Reason : The distance between the atoms of crystals is of the order of wavelength of X-rays.
|
(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. |
A PN- junction has a thickness of the order of
| (a) 1 cm | (b) 1 mm |
(c) 
|
(d) 
|
In the circuit shown, potential difference between X and Y will be
|
(a) Zero |
(b) 20 V |
(c) 60 V |
(d) 120 V |
Magnetic effect of current was discovered by
|
(a) Faraday |
(b) Oersted |
(c) Ampere |
(d) Bohr |
Assertion : The lightening conductor at the top of high building has sharp pointed ends.
Reason : The surface density of charge at sharp points is very high resulting in setting up of electric wind.
|
(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. |
Two coils A and B having turns 300 and 600 respectively are placed near each other, on passing a current of 3.0 ampere in A, the flux linked with A is 1.2 
and with B it is 9.0 
. The mutual inductance of the system is
|
(a) 2 × 10–5 henry |
(b) 3 × 10–5 henry |
(c) 4 × 10–5 henry |
(d) 6 × 10–5 henry |
