1
JEE Main 2021 (Online) 26th February Evening Shift
Numerical
+4
-1
27 similar drops of mercury are maintained at 10V each. All these spherical drops combine into a single big drop. The potential energy of the bigger drop is __________ times that of a smaller drop.
2
JEE Main 2021 (Online) 25th February Evening Shift
Numerical
+4
-1
The peak electric field produced by the radiation coming from the 8W bulb at a distance of 10 m is $${x \over {10}}\sqrt {{{{\mu _0}c} \over \pi }} {V \over m}$$. The efficiency of the bulb is 10% and it is a point source. The value of x is ___________.
3
JEE Main 2021 (Online) 25th February Evening Shift
Numerical
+4
-1
Two identical conducting spheres with negligible volume have 2.1 nC and $$-$$0.1 nC charges, respectively. They are brought into contact and then separated by a distance of 0.5 m. The electrostatic force acting between the spheres is __________ $$\times$$ 10$$-$$9 N.

[Given : $$4\pi {\varepsilon _0} = {1 \over {9 \times {{10}^9}}}$$ SI unit]
4
JEE Main 2021 (Online) 25th February Evening Shift
Numerical
+4
-1
Two small spheres each of mass 10 mg are suspended from a point by threads 0.5 m long. They are equally charged and repel each other to a distance of 0.20 m. The charge on each of the sphere is $${a \over {21}} \times {10^{ - 8}}$$C. The value of 'a' will be ___________. [Given g = 10 ms$$-$$2]
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