1
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
A copper rod of cross-sectional area A carries a uniform current I through it. At temperature T, if the volume charge density of the rod is $$\rho$$, how long will the changes take to travel a distance d ?
A
$${{2\rho \,d\,A} \over {\rm I}}$$
B
$${{2\rho \,d\,A} \over {{\rm I}\,T}}$$
C
$${{\rho \,d\,A} \over {{\rm I}\,}}$$
D
$${{\rho \,d\,A} \over {{\rm I}\,T}}$$
2
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
A constant voltages is applied between two ends of a metallic wire. If the length is halved and the radius of the wire is doubled, the rate of heat developed in the wire will be :
A
Doubled
B
Halved
C
Unchanged
D
Increased 8 times
3
JEE Main 2018 (Online) 15th April Morning Slot
+4
-1

In a meter bridge, as shown in the figure, it is given that resistance $$Y = 12.5\,\,\Omega$$ and that the balance is obtained at a distance $$39.5$$ $$cm$$ from end $$A$$ (by Jockey J). After interchanging the resistances $$X$$ and $$Y$$, a new balance point is found at a distance $${l_2}$$ from end $$A.$$ What are the value of $$X$$ and $${l_2}$$ ?
A
$$8.16\,\,\Omega$$ and $$60.5$$ $$cm$$
B
$$19.15\,\,\Omega$$ and $$39.5$$ $$cm$$
C
$$8.16\,\,\Omega$$ and $$39.5$$ $$cm$$
D
$$19.15\,\,\Omega$$ and $$60.5$$ $$cm$$
4
JEE Main 2018 (Online) 15th April Morning Slot
+4
-1
In the given circuit all resistances are of value $$R$$ $$ohm$$ each. The equivalent resistance between $$A$$ and $$B$$ is :

A
$$2R$$
B
$$3R$$
C
$${{5R} \over 3}$$
D
$${{5R} \over 2}$$
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