Explanation:
The Curie temperature(TC) is the temperature at which certain materials lose their permanent magnetic properties, to be replaced by induced magnetism, that is, they go from becoming ferromagnetic to paramagnetic.
Above curie temperature, ferromagnetic material behaves as paramegnetic material.
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A coil of wire having finite inductance and resistance has a conducting ring placed coaxially within it. The coil is connected to a battery at time t = 0, so that a time-dependent current 
starts flowing through the coil. If 
is the current induced in the ring. and B(t) is the magnetic field at the axis of the coil due to , then as a function of time (t > 0), the product I2 (t) B(t)
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(a) Increases with time |
(b) Decreases with time |
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(c) Does not vary with time |
(d) Passes through a maximum |
A circular coil of diameter 7cm has 24 turns of wire carrying current of 0.75A. The magnetic moment of the coil is
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(a) 6.9 |
(b) 2.3 |
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(c) |
(d) |
$\text{Mr}^2$
$\frac{1}{2}\text{Mr}^2$
$\frac{1}4{}\text{Mr}^2$
$\frac{2}{5}\text{Mr}^2$
The radioactivity of a certain radioactive element drops to 1/64 of its initial value in 30 seconds. Its half life is
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(a) 2 seconds |
(b) 4 seconds |
(c) 5 seconds |
(d) 6 seconds |
Assertion : The comet do not obey Kepler's laws of planetary motion
Reason : The comet do not have elliptical orbit
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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. |
|
(d) If the assertion and reason both are false. |
The ratio of real depth to apparent depth is called the the:
