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1

JEE Main 2021 (Online) 27th August Evening Shift

Numerical
The ratio of the equivalent resistance of the network (shown in figure) between the points a and b when switch is open and switch is closed is x : 8. The value of x is ___________.

Your Input ________

Answer

Correct Answer is 9

Explanation

$${R_{eq\,open}} = {{3R} \over 2}$$

$${R_{eq\,closed}} = 2 \times {{R \times 2R} \over {3R}} = {{4R} \over 3}$$

$${{{R_{eq\,open}}} \over {{R_{eq\,closed}}}} = {{3R} \over 2} \times {3 \over {4R}} = {9 \over 8}$$

$$\therefore$$ $$x = 9$$
2

JEE Main 2021 (Online) 27th August Morning Shift

Numerical
First, a set of n equal resistors of 10 $$\Omega$$ each are connected in series to a battery of emf 20V and internal resistance 10$$\Omega$$. A current I is observed to flow. Then, the n resistors are connected in parallel to the same battery. It is observed that the current is increased 20 times, then the value of n is ............... .
Your Input ________

Answer

Correct Answer is 20

Explanation

In series

$${R_{eq}} = nR = 10n$$

$${i_s} = {{20} \over {10 + 10n}} = {2 \over {1 + n}}$$

In parallel

$${R_{eq}} = {{10} \over n}$$

$${i_p} = {{20} \over {{{10} \over n} + 10}} = {{2n} \over {1 + n}}$$

$${{{i_p}} \over {{i_s}}} = 20$$

$${{\left( {{{2n} \over {1 + n}}} \right)} \over {\left( {{2 \over {1 + n}}} \right)}} = 20$$

$$n = 20$$
3

JEE Main 2021 (Online) 27th July Evening Shift

Numerical
For the circuit shown, the value of current at time t = 3.2 s will be _________ A.


[Voltage distribution V(t) is shown by Fig. (1) and the circuit is shown in Fig. (2)]
Your Input ________

Answer

Correct Answer is 1

Explanation

From graph voltage at t = 3.2 sec is 6 volt.


i = $${{6 - 5} \over 1}$$

$$ \Rightarrow $$ i = 1 A
4

JEE Main 2021 (Online) 25th July Morning Shift

Numerical
An electric bulb rated as 200 W at 100 V is used in a circuit having 200 V supply. The resistance 'R' that must be put in series with the bulb so that the bulb delivers the same power is _____________ $$\Omega$$.
Your Input ________

Answer

Correct Answer is 50

Explanation

Power, $$P = {{{V^2}} \over {{R_B}}}$$

$${R_B} = {{{V^2}} \over P} = {{100 \times 100} \over {200}}$$

$${R_B} = 50\Omega $$



To produce same power, same voltage (i.e. 100 V) should be across the bulb.

Hence, R = RB

R = 50 $$\Omega$$

Questions Asked from Current Electricity

On those following papers in Numerical
Number in Brackets after Paper Indicates No. of Questions
JEE Main 2021 (Online) 1st September Evening Shift (1)
JEE Main 2021 (Online) 31st August Evening Shift (2)
JEE Main 2021 (Online) 31st August Morning Shift (3)
JEE Main 2021 (Online) 27th August Evening Shift (1)
JEE Main 2021 (Online) 27th August Morning Shift (1)
JEE Main 2021 (Online) 27th July Evening Shift (1)
JEE Main 2021 (Online) 25th July Morning Shift (1)
JEE Main 2021 (Online) 22th July Evening Shift (1)
JEE Main 2021 (Online) 20th July Evening Shift (1)
JEE Main 2021 (Online) 18th March Evening Shift (2)
JEE Main 2021 (Online) 18th March Morning Shift (3)
JEE Main 2021 (Online) 17th March Evening Shift (2)
JEE Main 2021 (Online) 17th March Morning Shift (3)
JEE Main 2021 (Online) 16th March Evening Shift (2)
JEE Main 2021 (Online) 16th March Morning Shift (1)
JEE Main 2021 (Online) 26th February Morning Shift (1)
JEE Main 2021 (Online) 25th February Evening Shift (1)
JEE Main 2021 (Online) 25th February Morning Shift (1)
JEE Main 2021 (Online) 24th February Evening Shift (1)
JEE Main 2020 (Online) 4th September Evening Slot (1)
JEE Main 2020 (Online) 2nd September Evening Slot (1)
JEE Main 2020 (Online) 2nd September Morning Slot (1)
JEE Main 2020 (Online) 9th January Evening Slot (1)
JEE Main 2020 (Online) 8th January Evening Slot (1)
JEE Main 2020 (Online) 8th January Morning Slot (1)
JEE Main 2020 (Online) 7th January Evening Slot (2)

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