1
JEE Main 2021 (Online) 17th March Evening Shift
+4
-1
The four arms of a Wheatstone bridge have resistances as shown in the figure. A galvanometer of 15$$\Omega$$ resistance is connected across BD. Calculate the current through the galvanometer when a potential difference of 10V is maintained across AC.

A
4.87 $$\mu$$A
B
4.87 mA
C
2.44 mA
D
2.44 $$\mu$$A
2
JEE Main 2021 (Online) 17th March Morning Shift
+4
-1
A current of 10A exists in a wire of cross-sectional area of 5 mm2 with a drift velocity of 2 $$\times$$ 10$$-$$3 ms$$-$$1. The number of free electrons in each cubic meter of the wire is ___________.
A
625 $$\times$$ 1025
B
1 $$\times$$ 1023
C
2 $$\times$$ 1025
D
2 $$\times$$ 106
3
JEE Main 2021 (Online) 16th March Evening Shift
+4
-1
A resistor develops 500 J of thermal energy in 20 s when a current of 1.5A is passed through it. If the current is increased from 1.5A to 3A, what will be the energy developed in 20 s.
A
1000 J
B
2000 J
C
1500 J
D
500 J
4
JEE Main 2021 (Online) 16th March Morning Shift
+4
-1
A conducting wire of length 'l', area of cross-section A and electric resistivity $$\rho$$ is connected between the terminals of a battery. A potential difference V is developed between its ends, causing an electric current.

If the length of the wire of the same material is doubled and the area of cross-section is halved, the resultant current would be :
A
$$4{{VA} \over {\rho l}}$$
B
$${3 \over 4}{{VA} \over {\rho l}}$$
C
$${1 \over 4}{{VA} \over {\rho l}}$$
D
$${1 \over 4}{{\rho l} \over {VA}}$$
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