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NEET 2019
Exam
NEET
Year
2019
Subject
Physics
Chapter
Current Electricity

NEET 2019 · Physics · Current Electricity

In the circuits shown below, the readings of the voltmeters and the...

In the circuits shown below, the readings of the voltmeters and the ammeters will be,

In the circuits shown below, the readings of the voltmeters and the ammeters will be,

Options

  1. AV2>V1{V}_{2} > {V}_{1} and i1=i2{i}_{1} = {i}_{2}
  2. BV1=V2{V}_{1} = {V}_{2} and i1>i2{i}_{1} > {i}_{2}
  3. CV1=V2{V}_{1} = {V}_{2} and i1=i2{i}_{1} = {i}_{2}
  4. DV2>V1{V}_{2} > {V}_{1} and i1>i2{i}_{1} > {i}_{2}

Correct answer

C. V1=V2{V}_{1} = {V}_{2} and i1=i2{i}_{1} = {i}_{2}

Step-by-step solution

For an ideal voltmeter, resistance is infinite (RV=∞)\left({R}_{V} = \infty\right), so it will not draw any amount of current from the circuit and for ideal ammeter resistance is zero.

Then for the first figure R1=10Ω,RV=∞{R}_{1} = 10Ω, {R}_{V} = \infty and both are in a parallel arrangement, so

1Req=1R1+1RV⇒1Req=110+1∞⇒Req=10Ω\dfrac{1}{{R}_{eq}} = \dfrac{1}{{R}_{1}} + \dfrac{1}{{R}_{V}} ⇒ \dfrac{1}{{R}_{eq}} = \dfrac{1}{10} + \dfrac{1}{\infty} ⇒ {R}_{eq} = 10Ω

and current in the first circuit is, i1=V1Req=1010=1A{i}_{1} = \dfrac{{V}_{1}}{{R}_{eq}} = \dfrac{10}{10} = 1A

So, for the first circuit, ammeter and voltmeter readings are V1=10V,i1=1A{V}_{1} = 10V, {i}_{1} = 1A, respectively.

For the second figure voltmeter and resistant of 10Ω10Ω are in series and also connected parallel to another resistant of 10Ω10Ω. So, equivalent resistant is

1R′eq=1R1+1R2+RV⇒1R′eq=110+110+∞=110+0=110⇒R′eq=10Ω\dfrac{1}{{R}^{'}eq} = \dfrac{1}{{R}_{1}} + \dfrac{1}{{R}_{2} + {R}_{V}} ⇒ \dfrac{1}{{R}^{'}eq} = \dfrac{1}{10} + \dfrac{1}{10 + \infty} = \dfrac{1}{10} + 0 = \dfrac{1}{10} ⇒ {R}^{'}eq = 10Ω

∴∴ Current in the circuit is, i2=V2Req′=1010=1A{i}_{2} = {V}_{2}{R}_{eq}^{'} = \dfrac{10}{10} = 1A,

∴∴ Ammeter and voltmeter readings for the second circuit is V2=10V,i2=1A{V}_{2} = 10V, {i}_{2} = 1A

∴∴ For both the circuit is
V1=V2=10V,i1=i2=1A{V}_{1} = {V}_{2} = 10V, {i}_{1} = {i}_{2} = 1A

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