- AHigh coercivity and high retentivity.
- BHigh coercivity and low retentivity.
- CLow coercivity and low retentivity.
- DLow coercivity and high retentivity.
Explanation:
Alnico is used for making permanent magnet because it can be easily magnetised in external magnetic field and It will not lose its magnetic property due to its high coercivity and low retentivity.
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Six charges, three positive and three negative of equal magnitude are to be placed at the vertices of a regular hexagon such that the electric field at O is double the electric field when only one positive charge of same magnitude is placed at R. Which of the following arrangements of charges is possible for P, Q, R, S, T and U respectively

|
(a) +, -, +, -, -, + |
(b) +, -, +, -, +, - |
(c) +, +, -, +, -, - |
(d) -, +, +, -, +, - |
X-rays of
have frequency
|
(a) 3 |
(b) 3 |
(c) |
(d) |
Two coherent sources separated by distance d are radiating in phase having wavelength l. A detector moves in a big circle around the two sources in the plane of the two sources. The angular position of n = 4 interference maxima is given as
|
(a) |
(b) |
(c) |
(d) |
Bohr's atom model assumes
|
(a) The nucleus is of infinite mass and is at rest |
|
(b) Electrons in a quantized orbit will not radiate energy |
|
(c) Mass of electron remains constant |
|
(d) All the above conditions |
When the key K is pressed at time t = 0, which of the following statements about the current I in the resistor AB of the given circuit is true
|
(a) I = 2 mA at all t |
|
(b) I oscillates between 1 mA and 2mA |
|
(c) I = 1 mA at all t |
|
(d) At t = 0 , I = 2 mA and with time it goes to 1 mA |
A circular coil of radius 4 cm and of 20 turns carries a current of 3 amperes. It is placed in a magnetic field of intensity of 0.5 . The magnetic dipole moment of the coil is
|
(a) 0.15 |
(b) 0.3 |
(c) 0.45 |
(d) 0.6 |