1
JEE Main 2021 (Online) 20th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
Two small drops of mercury each of radius R coalesce to form a single large drop. The ratio of total surface energy before and after the change is :
A
$${2^{{1 \over 3}}}:1$$
B
$$1:{2^{{1 \over 3}}}$$
C
2 : 1
D
1 : 2
2
JEE Main 2021 (Online) 20th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
The magnetic susceptibility of a material of a rod is 499. Permeability in vacuum is 4$$\pi$$ $$\times$$ 10$$-$$7 H/m. Absolute permeability of the material of the rod is :
A
4$$\pi$$ $$\times$$ 10$$-$$4 H/m
B
2$$\pi$$ $$\times$$ 10$$-$$4 H/m
C
3$$\pi$$ $$\times$$ 10$$-$$4 H/m
D
$$\pi$$ $$\times$$ 10$$-$$4 H/m
3
JEE Main 2021 (Online) 20th July Evening Shift
Numerical
+4
-1
Change Language
A zener diode having zener voltage 8 V and power dissipation rating of 0.5 W is connected across a potential divider arranged with maximum potential drop across zener diode is as shown in the diagram. The value of protective resistance Rp is .................... $$\Omega$$.

JEE Main 2021 (Online) 20th July Evening Shift Physics - Semiconductor Question 87 English
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4
JEE Main 2021 (Online) 20th July Evening Shift
Numerical
+4
-1
Change Language
A body of mass 'm' is launched up on a rough inclined plane making an angle of 30$$^\circ$$ with the horizontal. The coefficient of friction between the body and plane is $${{\sqrt x } \over 5}$$ if the time of ascent is half of the time of descent. The value of x is __________.
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