- A0
- B$\pi$
- C$\frac{\pi}{2}$
- D$\frac{\pi}{4}$
Explanation:
The phase difference between electric and magnetic fields in an electromagnetic wave is$\pi$.
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Which of the following statement is true
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(a) The presence of a large magnetic flux through a coil maintains a current in the coil if the circuit is continuous |
|
(b) A coil of a metal wire kept stationary in a non-uniform magnetic field has an e.m.f. induced in it |
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(c) A charged particle enters a region of uniform magnetic field at an angle of 85° to the magnetic lines of force;the path of the particle is a circle |
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(d) There is no change in the energy of a charged particle moving in a magnetic field although a magnetic force is acting on it |
A semiconductor device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops almost to zero. The device may be
| (a) A P-type semiconductor | (b) An N-type semiconductor |
| (c) A PN-junction | (d) An intrinsic semiconductor |
The current in the arm CD of the circuit will be
|
(a) |
(b) |
(c) |
(d) |
For a given temperature difference, which of the following pairs will generate maximum thermo e.m.f.
|
(a) Antimony-bismuth |
(b) Silver-gold |
(c) Iron-copper |
(d) Lead-nickel |
Two thick wires and two thin wires, all of the same materials and same length form a square in the three different ways P, Q and R as shown in fig with current connection shown, the magnetic field at the centre of the square is zero in cases
|
(a) In P only |
(b) In P and Q only |
(c) In Q and R only |
(d) P and R only |
Starting with a sample of pure
of it decays into Zn in 15 min. The corresponding half-life is
| (a) 5 min |
(b) 7 |
(c) 10 min |
(d) 15 min |
Atomic number of a nucleus is Z and atomic mass is M. The number of neutron is
|
(a) M - Z |
(b) M |
(c) Z |
(d) M + Z |