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1

### 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) $$\Omega$$
2

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

Three capacitors C1 = 2$$\mu$$F, C2 = 6$$\mu$$F and C3 = 12$$\mu$$F are connected as shown in figure. Find the ratio of the charges on capacitors C1, C2 and C3 respectively : A
2 : 1 : 1
B
2 : 3 : 3
C
1 : 2 : 2
D
3 : 4 : 4

## Explanation (VD $$-$$ V) C2 + (VD $$-$$ 0) C3 = 0

(VD $$-$$ V) 6 + (VD $$-$$ 0) 12 = 0

VD $$-$$ V + 2VD = 0

VD = $${V \over 3}$$

q2 = (V $$-$$ VD) C2 = $$\left( {V - {V \over 3}} \right)$$ (6 $$\mu$$F)

q2 = (4V) $$\mu$$F

q3 = (VD $$-$$ 0) C3 = $${{V \over 3}}$$ $$\times$$ 12$$\mu$$F = 4V$$\mu$$F

q1 = (V $$-$$ 0) C1 = V(2$$\mu$$F)

q1 : q2 : q3 = 2 : 4 : 4

q1 : q2 : q3 = 1 : 2 : 2
3

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

Five identical cells each of internal resistance 1$$\Omega$$ and emf 5V are connected in series and in parallel with an external resistance 'R'. For what value of 'R', current in series and parallel combination will remain the same?
A
1 $$\Omega$$
B
25 $$\Omega$$
C
5 $$\Omega$$
D
10 $$\Omega$$

## Explanation

$${i_1} = {{25} \over {5 + R}}$$

$${i_2} = {5 \over {R + {1 \over 5}}}$$

$${i_1} = {i_2} \Rightarrow 5\left( {R + {1 \over 5}} \right) = 5 + R$$

4R = R

R = 1$$\Omega$$
4

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

Calculate the amount of charge on capacitor of 4$$\mu$$F. The internal resistance of battery is 1$$\Omega$$ : A
8 $$\mu$$C
B
zero
C
16 $$\mu$$C
D
4 $$\mu$$C

## Explanation

On simplifying circuit we get No current in upper wire.

$$\therefore$$ $${V_{AB}} = {5 \over {4 + 1}} \times 4 = 4$$ v

$$\therefore$$ $$\theta$$ = (Ceq)v

$$\Rightarrow$$ 2 $$\times$$ 4 = 8 $$\mu$$C

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