 ### JEE Mains Previous Years Questions with Solutions

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1

### JEE Main 2021 (Online) 31st August Morning Shift

Two particles A and B having charges 20$$\mu$$C and $$-$$5$$\mu$$C respectively are held fixed with a separation of 5 cm. At what position a third charged particle should be placed so that it does not experience a net electric force? A
At 5 cm from 20 $$\mu$$C on the left side of system
B
At 5 cm from $$-$$5 $$\mu$$C on the right side
C
At 1.25 cm from $$-$$5 $$\mu$$C between two charges
D
At midpoint between two charges

## Explanation

Null point is possible only right side of $$-$$5 $$\mu$$C $${E_N} = + {{k( - 5\mu C)} \over {{x^2}}} + {{k(20\mu C)} \over {{{(5 + x)}^2}}} = 0$$

x = 5 cm

$$\therefore$$ Option (b) is correct.
2

### JEE Main 2021 (Online) 27th August Evening Shift

For full scale deflection of total 50 divisions, 50 mV voltage is required in galvanometer. The resistance of galvanometer if its current sensitivity is 2 div/mA will be :
A
1$$\Omega$$
B
5$$\Omega$$
C
4$$\Omega$$
D
2$$\Omega$$

## Explanation

$${I_{\max }} = {{50} \over 2} = 25$$ mA

$$R = {V \over I} = {{50mV} \over {25mA}} = 2\Omega$$
3

### JEE Main 2021 (Online) 27th August Evening Shift

The Colour coding on a carbon resistor is shown in the given figure. The resistance value of the given resistor is : A
(5700 $$\pm$$ 285) $$\Omega$$
B
(7500 $$\pm$$ 750) $$\Omega$$
C
(5700 $$\pm$$ 375) $$\Omega$$
D
(7500 $$\pm$$ 375) $$\Omega$$

## Explanation

R = 75 $$\times$$ 102 $$\pm$$ 5% of 7500

R = (7500 $$\pm$$ 375) $$\Omega$$
4

### JEE Main 2021 (Online) 26th August Evening Shift

If you are provided a set of resistances 2$$\Omega$$, 4$$\Omega$$, 6$$\Omega$$ and 8$$\Omega$$. Connect these resistances so as to obtain an equivalent resistance of $${{46} \over 3}$$$$\Omega$$.
A
4$$\Omega$$ and 6$$\Omega$$ are in parallel with 2$$\Omega$$ and 8$$\Omega$$ in series
B
6$$\Omega$$ and 8$$\Omega$$ are in parallel with 2$$\Omega$$ and 4$$\Omega$$ in series
C
2$$\Omega$$ and 6$$\Omega$$ are in parallel with 4$$\Omega$$ and 8$$\Omega$$ in series
D
2$$\Omega$$ and 4$$\Omega$$ are in parallel with 6$$\Omega$$ and 8$$\Omega$$ in series

## Explanation ### Joint Entrance Examination

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NEET

Class 12