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
Out of Syllabus
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
3
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
4
JEE Main 2020 (Online) 9th January Morning Slot
+4
-1
In the given circuit diagram, a wire is joining points B and D. The current in this wire is :
A
4 A
B
2 A
C
zero
D
0.4 A
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