Electrostatics & Capacitors · JEE Main previous year questions

2005 8 questions

1. Q1102005 · 28 Apr 2005 · Shift 1

   Two point charges $+8q$ and $-2q$ are located at $x=0$ and $x=L$ respectively. The location of a point on the $x$ axis at which the net electric field due to these two point charges is zero is

   1. A.$\frac{L}{4}$
   2. B.$2L$
   3. C.$4L$
   4. D.$8L$
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   Answer: B

2. Q1112005 · 28 Apr 2005 · Shift 1

   Two thin wire rings each having a radius $R$ are placed at a distance $d$ apart with their axes coinciding. The charges on the two rings are $+q$ and $-q$. The potential difference between the centres of the two rings is

   1. A.$\frac{q}{2\pi {ϵ}_0}\left[\frac{1}{R}-\frac{1}{\sqrt{R^2+d^2}}\right]$
   2. B.$\frac{qR}{4\pi {ϵ}_0{d}^2}$
   3. C.$\frac{q}{4\pi {ϵ}_0}\left[\frac{1}{R}-\frac{1}{\sqrt{R^2+d^2}}\right]$
   4. D.$\mathrm{zero}$
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   Answer: A

3. Q1122005 · 28 Apr 2005 · Shift 1

   A parallel plate capacitor is made by stacking $n$ equally spaced plates connected alternatively. If the capacitance between any two adjacent plates is '$C$' then the resultant capacitance is

   1. A.$(n+1)C$
   2. B.$(n-1)C$
   3. C.$nC$
   4. D.$C$
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   Answer: B

4. Q1132005 · 28 Apr 2005 · Shift 1
   
   1. A.$\cot \theta$
   2. B.$\cos \theta$
   3. C.$\tan \theta$
   4. D.$\sin \theta$
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   Answer: C

5. Q1142005 · 28 Apr 2005 · Shift 1

   A fully charged capacitor has a capacitance '$C$'. It is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity '$s$' and mass '$m$'. If the temperature of the block is raised by '$\Delta T$', the potential difference '$v$' across the capacitor is

   1. A.$\frac{mC\Delta T}{s}$
   2. B.$\sqrt{\frac{2mC\Delta T}{s}}$
   3. C.$\sqrt{\frac{2ms\Delta T}{C}}$
   4. D.$\frac{ms\Delta T}{C}$
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   Answer: C

6. Q1202005 · 28 Apr 2005 · Shift 1

   Two voltmeters, one of copper and another of silver, are joined in parallel. When a total charge $q$ flows through the voltmeters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are $Z_1$ and $Z_2$ respectively the charge which flows through the silver voltmeter is

   1. A.$\frac{q}{1+\frac{Z_2}{Z_1}}$
   2. B.$\frac{q}{1+\frac{Z_1}{Z_2}}$
   3. C.$q\frac{Z_2}{Z_1}$
   4. D.$q\frac{Z_1}{Z_2}$
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   Answer: A

7. Q1262005 · 28 Apr 2005 · Shift 1

   A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity then

   1. A.its velocity will increase
   2. B.Its velocity will decrease
   3. C.it will turn towards left of a direction of motion
   4. D.it will turn towards right of direction of motion
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   Answer: B

8. Q1272005 · 28 Apr 2005 · Shift 1

   The self inductance of the motor of an electric fan is $10\mathrm{H}$. In order to impart maximum power at $50\mathrm{Hz}$, it should be connected to a capacitance of

   1. A.$8\mu \mathrm{F}$
   2. B.$4\mu \mathrm{F}$
   3. C.$2\mu \mathrm{F}$
   4. D.$1\mu \mathrm{F}$
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   Answer: D