Electrostatics & Capacitors · JEE Main previous year questions

2004 6 questions

1. Q1032004 · 24 Apr 2004 · Shift 1

   Two spherical conductors $B$ and $C$ having equal radii and carrying equal charges on them repel each other with a force $F$ when kept apart at some distance. A third spherical conductor having same radius as that of $B$ but uncharged is brought in contact with $B$, then brought in contact with $C$ and finally removed away from both. The new force of repulsion between $B$ and $C$ is

   1. A.$F/8$
   2. B.$3F/4$
   3. C.$F/4$
   4. D.$3F/8$
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   Answer: D

2. Q1042004 · 24 Apr 2004 · Shift 1

   A charged particle ${}^{\prime }{q}^{\prime }$ is shot towards another charged particle ${}^{\prime }{Q}^{\prime }$ which is fixed, with a speed ${}^{\prime }{v}^{\prime }$. It approaches ${}^{\prime }{Q}^{\prime }$ upto a closest distance $r$ and then returns. If $q$ were given a speed of ${}^{\prime }2v^{\prime }$ the closest distance of approach would be

   1. A.$r/2$
   2. B.$2r$
   3. C.$r$
   4. D.$r/4$
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   Answer: D

3. Q1052004 · 24 Apr 2004 · Shift 1

   Four charges equal to -$Q$ are placed at the four corners of a square and a charge $q$ is at its center. If the system is in equilibrium the value of $q$ is

   1. A.$-\frac{Q}{2}(1+2\sqrt{2})$
   2. B.$\frac{Q}{4}(1+2\sqrt{2})$
   3. C.$-\frac{Q}{4}(1+2\sqrt{2})$
   4. D.$\frac{Q}{2}(1+2\sqrt{2})$
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   Answer: B

4. Q1062004 · 24 Apr 2004 · Shift 1

   A charged oil drop is suspended in a uniform field of $3\times 10^{4}v/m$ so that it neither falls nor rises. The charge on the drop will be (Take the mass of the charge $=9.9\times 10^{-15}\mathrm{kg}$ and $g=10m/{\mathrm{s}}^2$)

   1. A.$1.6\times 10^{-18}\mathrm{C}$
   2. B.$3.2\times 10^{-18}\mathrm{C}$
   3. C.$3.3\times 10^{-18}\mathrm{C}$
   4. D.$4.8\times 10^{-18}\mathrm{C}$
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   Answer: C

5. Q1142004 · 24 Apr 2004 · Shift 1

   The electrochemical equivalent of a metal is $3.3\times 10^{-7}\mathrm{kg}$ per Coulomb. The mass of the metal liberated at the cathode when a $3\mathrm{A}$ current is passed for $2$ seconds will be

   1. A.$6.6\times 10^{-7}\mathrm{kg}$
   2. B.$9.9\times 10^{-7}\mathrm{kg}$
   3. C.$19.8\times 10^{-7}\mathrm{kg}$
   4. D.$1.1\times 10^{-7}\mathrm{kg}$
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   Answer: C

6. Q1332004 · 24 Apr 2004 · Shift 1

   An electromagnetic wave of frequency $v=3.0\mathrm{MHz}$ passes from vacuum into a dielectric medium with permittivity $ϵ=4.0$. Then

   1. A.wave length is halved and frequency remains unchanged
   2. B.wave length is doubled and the frequency becomes half
   3. C.wave length is doubled and the frequency remains unchanged
   4. D.wave length and frequency both remain unchanged.
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   Answer: A