- A[L-2 T A].
- B[L-1 T A].
- C[L T A].
- DNone.
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One metre length of wire carries a constant current. The wire is bent to form a circular loop. The magnetic field at the centre of this loop is B. The same is now bent to form a circular loop of smaller radius to have four turns in the loop. The magnetic field at the centre of this new loop is
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(a) 4 B |
(b) 16 B |
(c) B/2 |
(d) B/4 |
Light of frequency 8
is incident on a substance of photoelectric work function 6.125eV. The maximum kinetic energy of the emitted photoelectrons is
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(a) 17eV |
(b) 22eV |
(c) 27eV |
(d) 37eV |
The continuous x-ray spectrum obtained from a Coolidge tube is of the form
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(a)
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(b)
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(b)
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(d)
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Assertion : The force with which one plate of a parallel plate capacitor is attracted towards the other plate is equal to square of surface density per e per unit area.
Reason : The electric field due to one charged plate of the capacitor at the location of the other is equal to surface density per e.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
An external resistance R is connected to a battery of e.m.f. V and internal resistance r. The joule heat produced in resistor R is maximum when R is equal to
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(a) r |
(b) |
(c) 2r |
(d) Infinitely large |