Current Electricity · JEE Main previous year questions

2018 10 questions

1. Q422018 · 16 Apr 2018 · Shift 1

   A heating element has a resistance of $100\Omega$ at room temperature. When it is connected to a supply of 220 V, a steady current of 2 A passes in it and temperature is $500^{\circ }\text{C}$ more than room temperature. What is the temperature coefficient of resistance of the heating element ?

   1. A.$0.5\times 10^{-4}{}^{\circ }{\text{C}}^{-1}$
   2. B.$5\times 10^{-4}{}^{\circ }{\text{C}}^{-1}$
   3. C.$1\times 10^{-4}{}^{\circ }{\text{C}}^{-1}$
   4. D.$2\times 10^{-4}{}^{\circ }{\text{C}}^{-1}$
   Show answer

   Answer: D

2. Q432018 · 16 Apr 2018 · Shift 1

   A galvanometer with its coil resistance $25\Omega$ requires a current of 1 mA for its full deflection. In order to construct an ammeter to read upto a current of 2 A, the approximate value of the shunt resistance should be :

   1. A.$2.5\times 10^{-3}\Omega$
   2. B.$1.25\times 10^{-2}\Omega$
   3. C.$1.25\times 10^{-3}\Omega$
   4. D.$2.5\times 10^{-2}\Omega$
   Show answer

   Answer: B

3. Q512018 · 16 Apr 2018 · Shift 1

   In a circuit for finding the resistance of a galvanometer by half deflection method, a 6 V battery and a high resistance of $11\text{k}\Omega$ are used. The figure of merit of the galvanometer is $60\mu A/\text{division}$. In the absence of shunt resistance, the galvanometer produces a deflection of $\theta =9$ divisions when current flows in the circuit. The value of the shunt resistance that can cause the deflection of $\theta /2$, is closest to :

   1. A.$500\Omega$
   2. B.$220\Omega$
   3. C.$55\Omega$
   4. D.$110\Omega$
   Show answer

   Answer: D

4. Q502018 · 15 Apr 2018 · Shift 1
   
   1. A.$8.16\Omega$ and $60.5cm$
   2. B.$19.15\Omega$ and $39.5cm$
   3. C.$8.16\Omega$ and $39.5cm$
   4. D.$19.15\Omega$ and $60.5cm$
   Show answer

   Answer: A

5. Q562018 · 15 Apr 2018 · Shift 1
   
   1. A.$2R$
   2. B.$3R$
   3. C.$\frac{5R}{3}$
   4. D.$\frac{5R}{2}$
   Show answer

   Answer: A

6. Q592018 · 15 Apr 2018 · Shift 1

   In a common emitter configuration with suitable bias, it is given that $R_L$ is the load resistance and $R_{BE}$ is small signal dynamic resistance (input side). Then, voltage gain, current gain and power gain are given, respectively, by : $\beta$ is current gain, ${\text{I}}_B,{\text{I}}_C$ and ${\text{I}}_E$ are respectively base, collector and emitter currents.

   1. A.$\beta \frac{R_L}{R_{BE}},\frac{\Delta {\text{I}}_C}{\Delta {\text{I}}_B},{\beta }^2\frac{R_L}{R_{BE}}$
   2. B.$\beta \frac{R_L}{R_{BE}},\frac{\Delta {\text{I}}_E}{\Delta {\text{I}}_B},{\beta }^2\frac{R_L}{R_{BE}}$
   3. C.${\beta }^2\frac{R_L}{R_{BE}},\frac{\Delta {\text{I}}_C}{\Delta {\text{I}}_E},{\beta }^2\frac{R_L}{R_{BE}}$
   4. D.${\beta }^2\frac{R_L}{R_{BE}},\frac{\Delta {\text{I}}_C}{\Delta {\text{I}}_B},\beta \frac{R_L}{R_{BE}}$
   Show answer

   Answer: A

7. Q462018 · 8 Apr 2018 · Shift 1

   Two batteries with e.m.f 12 V and 13 V are connected in parallel across a load resistor of $10\Omega$. The internal resistances of the two batteries are $1\Omega$ and $2\Omega$ respectively. The voltage across the load lies between :

   1. A.11.7 V and 11.8 V
   2. B.11.6 V and 11.7 V
   3. C.11.5 V and 11.6 V
   4. D.11.4 V and 11.5 V
   Show answer

   Answer: C

8. Q472018 · 8 Apr 2018 · Shift 1

   On interchanging the resistances, the balance point of a meter bridge shifts to the left by 10 cm. The resistance of their series combination is $1\text{k}\Omega$. How much was the resistance on the left slot before interchanging the resistances?

   1. A.$910\Omega$
   2. B.$990\Omega$
   3. C.$505\Omega$
   4. D.$550\Omega$
   Show answer

   Answer: D

9. Q502018 · 8 Apr 2018 · Shift 1

   In an a.c. circuit, the instantaneous e.m.f. and current are given by $e=100\sin 30\text{t}$ $i=20\sin \left(30\text{t}-\frac{\pi }{4}\right)$ In one cycle of a.c., the average power consumed by the circuit and the wattless current are, respectively

   1. A.50, 0
   2. B.50, 10
   3. C.$\frac{1000}{\sqrt{2}},10$
   4. D.$\frac{50}{\sqrt{2}}$
   Show answer

   Answer: C

10. Q602018 · 8 Apr 2018 · Shift 1

    In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across 52 cm of the potentiometer wire. If the cell is shunted by a resistance of $5\Omega$, a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell.

    1. A.$2.5\Omega$
    2. B.$1\Omega$
    3. C.$1.5\Omega$
    4. D.$2\Omega$
    Show answer

    Answer: C