For protecting a sensitive equipment from the external magnetic field, it should be
|
(a) Placed inside an aluminium cane |
|
(b) Placed inside an iron cane |
|
(c) Wrapped with insulation around it when passing current through it |
|
(d) Surrounded with fine copper sheet |
(b) Placed inside an iron cane
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20 ampere current is flowing in a long straight wire. The intensity of magnetic field at a distance 10 cm from the wire will be
|
(a) 4 × 10–5 Wb/m2 |
(b) 9 × 10–5 Wb/m2 |
(c) 8 × 10–5 Wb/m2 |
(d) 6 × 10–5 Wb/m2 |
Three observers A, B and C measure the speed of light coming from a source to be 
and 
. The observer A moves towards the source, the observer C moves away from the source with the same speed. The observer B stays stationary. the surrounding space is vacuum every where. Then
(a) 
|
(b) 
|
(c) 
|
(d) 
|
Starting with a sample of pure 
of it decays into Zn in 15 min. The corresponding half-life is
| (a) 5 min |
(b) 7  min
|
(c) 10 min |
(d) 15 min |
A coil has 1,000 turns and 500 cm2 as its area. The plane of the coil is placed at right angles to a magnetic induction field of 2
. The coil is rotated through 180° in 0.2 seconds. The average e.m.f. induced in the coil, in milli-volts, is
|
(a) 5 |
(b) 10 |
(c) 15 |
(d) 20 |
Which statement is correct
|
(a) N-type germanium is negatively charged and P-type germanium is positively charged |
|
(b) Both N-type and P-type germanium are neutral |
|
(c) N-type germanium is positively charged and P-type germanium is negatively charged |
|
(d) Both N-type and P-type germanium are negatively charged |
A charge of 5 C is given a displacement of 0.5 m. The work done in the process is 10 J. The potential difference between the two points will be
|
(a) 2 V |
(b) 0.25 V |
(c) 1V |
(d) 25 V |
If the potential difference applied across X-ray tube is V volts, then approximately minimum wavelength of the emitted X-rays will be
|
(a) |
(b) |
(c) |
(d) |
The relaxation time in conductors
|
(a) Increases with the increase of temperature |
|
(b) Decreases with the increase of temperature |
|
(c) It does not depend on temperature |
|
(d) All of sudden changes at 400 K |
