Important PYQs on Current Electricity for NEET Physics

Q 1 :
The terminal voltage of the battery, whose emf is 10 V and internal resistance 1 $Ω$ , when connected through an external resistance of 4 $Ω$ as shown in the figure is [2024]

[IMAGE 185]----------------------------------

4 V
6 V
8 V
10 V

1

2

3

4

(3)

Current in the given circuit

$I = \frac{10}{4 + 1} = \frac{10}{5} = 2 A$

Terminal voltage, $V = E - I r = 10 - 2 \times 1 = 8$ $V$

Q 2 :
10 resistors, each of resistance $R$ are connected in series to a battery of emf $E$ and negligible internal resistance. Then those are connected in parallel to the same battery, the current is increased $n$ times. The value of $n$ is [2023]

1
1000
10
100

1

2

3

4

(4)

Net resistance in series combination,

$R_{N} = R_{1} + R_{2} + \dots + R_{10}$

$= 10 + 10 + \dots + 10 = 10 \times 10 = 100 Ω$ ...(i)

Same number of resistors and each of same magnitude connected in parallel combination,

$R'_{N} = {(\frac{1}{R_{1}} + \frac{1}{R_{2}} + \dots + \frac{1}{R_{10}})}^{- 1}$

$= {(\frac{1 + 1 + \dots + 1}{10})}^{- 1} = \frac{10}{10} = 1 Ω$ ...(ii)

Using (i) and (ii), $\frac{I'}{I} = \frac{V . R_{N}}{R'_{N} . V} = \frac{100}{1}$

Thus, option (4) is correct.

Q 3 :
A set of $n$ equal resistors, of value $R$ each, are connected in series to a battery of emf $E$ and internal resistance $R$ . The current drawn is $I$ . Now, the $n$ resistors are connected in parallel to the same battery. Then the current drawn from battery becomes $10 I$ . The value of $n$ is [2018]

10
11
20
9

1

2

3

4

(1)

Current drawn from a battery when $n$ resistors are connected in series is

$I = \frac{E}{n R + R}$ ...(i)

Current drawn from same battery when $n$ resistors are connected in parallel is

$10 I = \frac{E}{\frac{R}{n} + R}$ ...(ii)

On dividing eqn. (ii) by (i), $10 = \frac{(n + 1) R}{(\frac{1}{n + 1}) R}$

After solving the equation, $n = 10$

Topic Question Set

Q 1 :
The terminal voltage of the battery, whose emf is 10 V and internal resistance 1 $Ω$ , when connected through an external resistance of 4 $Ω$ as shown in the figure is [2024]

[IMAGE 185]----------------------------------

Q 2 :
10 resistors, each of resistance $R$ are connected in series to a battery of emf $E$ and negligible internal resistance. Then those are connected in parallel to the same battery, the current is increased $n$ times. The value of $n$ is [2023]

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Topic Question Set

Q 1 : The terminal voltage of the battery, whose emf is 10 V and internal resistance 1Ω, when connected through an external resistance of 4Ω as shown in the figure is [2024] [IMAGE 185]----------------------------------

Q 2 : 10 resistors, each of resistance R are connected in series to a battery of emf E and negligible internal resistance. Then those are connected in parallel to the same battery, the current is increased n times. The value of n is [2023]

Q 3 : A set of n equal resistors, of value R each, are connected in series to a battery of emf E and internal resistance R. The current drawn is I. Now, the n resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10I. The value of n is [2018]

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Q 1 :
The terminal voltage of the battery, whose emf is 10 V and internal resistance 1 $Ω$ , when connected through an external resistance of 4 $Ω$ as shown in the figure is [2024]

[IMAGE 185]----------------------------------

Q 2 :
10 resistors, each of resistance $R$ are connected in series to a battery of emf $E$ and negligible internal resistance. Then those are connected in parallel to the same battery, the current is increased $n$ times. The value of $n$ is [2023]