Electrostatics & Capacitors · JEE Main previous year questions

2012 8 questions

1. Q442012 · 26 May 2012 · Shift 1
   
   1. A.
   2. B.
   3. C.
   4. D.
   Show answer

   Answer: C

2. Q452012 · 26 May 2012 · Shift 1

   This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: It is not possible to make a sphere of capacity 1 farad using a conducting material. Statement 2: It is possible for earth as its radius is $6.4\times 10^6\mathrm{m}$.

   1. A.Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement 1.
   2. B.Statement 1 is false, Statement 2 is true.
   3. C.Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement 1.
   4. D.Statement 1 is true, Statement 2 is false.
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   Answer: D

3. Q462012 · 26 May 2012 · Shift 1

   The capacitor of an oscillatory circuit is enclosed in a container. When the container is evacuated, the resonance frequency of the circuit is $10\mathrm{kHz}$. When the container is filled with a gas, the resonance frequency changes by $50\mathrm{Hz}$. The dielectric constant of the gas is

   1. A.$1.001$
   2. B.$2.001$
   3. C.$1.01$
   4. D.$3.01$
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   Answer: C

4. Q502012 · 26 May 2012 · Shift 1

   A radio transmitter transmits at $830\mathrm{kHz}$. At a certain distance from the transmitter magnetic field has amplitude $4.82\times 10^{-11}\mathrm{T}$. The electric field and the wavelength are respectively

   1. A.$0.014N/C,36\mathrm{m}$
   2. B.$0.14N/C,36\mathrm{m}$
   3. C.$0.14N/C,360\mathrm{m}$
   4. D.$0.014N/C,360\mathrm{m}$
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   Answer: D

5. Q442012 · 12 May 2012 · Shift 1

   A series combination of $n_1$ capacitors, each of capacity $C_1$ is charged by source of potential difference $4V$. When another parallel combination of $n_2$ capacitors each of capacity $C_2$ is charged by a source of potential difference $V$, it has the same total energy stored in it as the first combination has. The value of $C_2$ in terms of $C_1$ is then

   1. A.$16\frac{n_2}{n_1}{C}_1$
   2. B.$\frac{2C_1}{n_1{n}_2}$
   3. C.$2\frac{n_2}{n_1}{C}_1$
   4. D.$\frac{16C_1}{n_1{n}_2}$
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   Answer: D

6. Q472012 · 7 May 2012 · Shift 1

   The electric potential $V(x)$ in a region around the origin is given by $V(x)=4x^2$ volts. The electric charge enclosed in a cube of $1\mathrm{m}$ side with its centre at the origin is (in coulomb)

   1. A.$8{\epsilon }_0$
   2. B.$-4{\epsilon }_0$
   3. C.0
   4. D.$-8{\epsilon }_0$
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   Answer: D

7. Q482012 · 7 May 2012 · Shift 1
   
   1. A.No charge flows in (a) but charge flows from $R$ to $L$ in (b)
   2. B.Charges flow from $L$ to $R$ in both (a) and (b)
   3. C.Charges flow from $R$ to $L$ in (a) and from $L$ to $R$ in (b)
   4. D.No charge flows in (a) but charge flows from $L$ to $R$ in (b)
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   Answer: C

8. Q512012 · 7 May 2012 · Shift 1

   The velocity of certain ions that pass undeflected through crossed electric field $E=7.7kV/m$ and magnetic field $B=0.14\mathrm{T}$ is

   1. A.$18km/s$
   2. B.$77km/s$
   3. C.$55km/s$
   4. D.$1078km/s$
   Show answer

   Answer: C