1
JEE Main 2020 (Online) 3rd September Morning Slot
+4
-1
Model a torch battery of length $$l$$ to be made up of a thin cylindrical bar of radius ‘a’ and a concentric thin cylindrical shell of radius ‘b’ filled in between with an electrolyte of resistivity $$\rho$$ (see figure). If the battery is connected to a resistance of value R, the maximum Joule heating in R will take place for :
A
$$R = {{2\rho } \over {\pi l}}\ln \left( {{b \over a}} \right)$$
B
$$R = {\rho \over {\pi l}}\ln \left( {{b \over a}} \right)$$
C
$$R = {\rho \over {2\pi l}}\ln \left( {{b \over a}} \right)$$
D
$$R = {\rho \over {2\pi l}}\left( {{b \over a}} \right)$$
2
JEE Main 2020 (Online) 2nd September Evening Slot
+4
-1
A small point mass carrying some positive charge on it, is released from the edge of a table. There is a uniform electric field in this region in the horizontal direction. Which of the following options then correctly describe the trajectory of the mass?
(Curves are drawn schematically and are not to scale).
A
B
C
D
3
JEE Main 2020 (Online) 2nd September Evening Slot
+4
-1
A potentiometer wire PQ of 1 m length is connected to a standard cell E1. Another cell E2 of emf 1.02 V is connected with a resistance ‘r’ and switch S (as shown in figure). With switch S open, the null position is obtained at a distance of 49 cm from Q. The potential gradient in the potentiometer wire is :
A
0.04 V/cm
B
0.01 V/cm
C
0.02 V/cm
D
0.03 V/cm
4
JEE Main 2020 (Online) 2nd September Morning Slot
+4
-1
Consider four conducting materials copper, tungsten, mercury and aluminium with resistivity $$\rho$$C, $$\rho$$T, $$\rho$$M and $$\rho$$A respectively. Then :
A
$$\rho$$C > $$\rho$$A > $$\rho$$T
B
$$\rho$$M > $$\rho$$A > $$\rho$$C
C
$$\rho$$A > $$\rho$$T > $$\rho$$C
D
$$\rho$$A > $$\rho$$M > $$\rho$$C
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Modern Physics
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