1
JEE Main 2017 (Online) 9th April Morning Slot
+4
-1
A uniform wire of length 1 and radius r has a resistance of 100 $$\Omega$$. It is recast into a wire of radius $${r \over 2}.$$ The resistance of new wire will be :
A
1600 $$\Omega$$
B
400 $$\Omega$$
C
200 $$\Omega$$
D
100 $$\Omega$$
2
JEE Main 2017 (Online) 9th April Morning Slot
+4
-1
In a meter bridge experiment resistances are connected as shown in the figure. Initially resistance P = 4 $$\Omega$$ and the neutral point N is at 60 cm from A. Now an unknown resistance R is connected in series to P and the new position of the neutral point is at 80 cm from A. The value of unknown resistance R is :

A
$${{33} \over 5}\,\Omega$$
B
6 $$\,\Omega$$
C
7 $$\,\Omega$$
D
$${{20} \over 3}\,\Omega$$
3
JEE Main 2017 (Online) 9th April Morning Slot
+4
-1
The figure shows three circuits I, II and III which are connected to a 3V battery. If the powers dissipated by the configurations I, II and III are P1 , P2 and P3 respectively, then :

A
P1 > P2 > P3
B
P1 > P3 > P2
C
P2 > P1 > P3
D
P3 > P2 > P1
4
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
Out of Syllabus
A potentiometer PQ is set up to compare two resistances as shown in the figure. The ammeter A in the circuit reads 1.0 A when two way key K3 is open. The balance point is at a length $$\ell$$1 cm from P when two way key K3 is plugged in between 2 and 1, while the balance point is at a length $$\ell$$2 cm from P when key K3 is plugged in between 3 and 1. The ratio of two resistances $${{{R_1}} \over {{R_2}}}$$, is found to be :

A
$${{{l_1}} \over {{l_1} + {l_2}}}$$
B
$${{{l_2}} \over {{l_2} - {l_1}}}$$
C
$${{{l_1}} \over {{l_1} - {l_2}}}$$
D
$${{{l_1}} \over {{l_2} - {l_1}}}$$
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