Emf and Emf Devices

Q. The figure shows a circuit that contains four identical resistors with resistance $R=2.0\Omega$. Two identical inductors with inductance $L=2.0\text{mH}$ and an ideal battery with emf $E=9\text{V}$. The current$\left(i\right)$ just after the switch ${}^{\prime }{s}^{\prime }$ is closed will be:

1. $9\text{A}$
2. $3\text{A}$
3. $2.25\text{A}$
4. $3.37\text{A}$

Q.
In the given figure, all the batteries are ideal. Find the value of $i$ (in ampere)

Q. In the circuit shown, current flowing through $25\text{V}$ cell in amperes is: (answer the nearest integer)

Q. Find the e.m.f. (in $V$) ${\epsilon }_1$ and ${\epsilon }_2$ in the circuit as shown in the figure. Also find the potential
difference (in $V$) of point '$a$' relative to point '$b$'.
${\epsilon }_1$ =
${\epsilon }_2$ =
$V_a-V_b$ =

Q. In the given circuit, find the ratio of $i_1$ and $i_2$. $i_1$ is the initial (at $t=0$) current, and $i_2$ is the steady state (at $t=\infty )$ current through the battery:

1. $2:5$
2. $4:5$
3. $5:2$
4. $3:2$

Q. Under what conditions current passing through a resistance $R$ can be increased by short-circuiting the battery of emf $E_2$. The internal resistances of the two batteries are $r_1$ and $r_2$ respectively.

1. $E_2{r}_1>E_1(R+r_2)$
2. $E_1{r}_2>E_2(R+r_1)$
3. $E_2{r}_2<E_1(R+r_2)$
4. $E_1{r}_1<E_2(R+r_1)$

Q. Two resistors of $10\Omega$ and $20\Omega$, and an ideal inductor of $10\text{H}$ are connected to a $2V$ battery as shown. The key $K$ is closed at time $t=0$. At the initial $(t=0)$ and final $(t\to \infty )$, the currents through the battery are

1. $\frac{1}{15}\text{A},\frac{1}{10}\text{A}$
2. $\frac{1}{10}\text{A},\frac{1}{15}\text{A}$
3. $\frac{1}{10}\text{A},\frac{1}{10}\text{A}$
4. $\frac{1}{15}\text{A},\frac{3}{10}\text{A}$

Q. In the given branch $AB$ of a circuit a current $I=(10t+5)A$ is flowing, where $t$ is time in second. At $t=0$, the potential difference between points $A$ and $B$ $(V_A-V_B)$ is :

1. $15V$
2. $-5V$
3. $-15V$
4. $5V$

Q. Find the dimensions of RC (R = Resistance, C = Capacitance).

Q. In the given circuit with steady current, the potential drop across the capacitor must be :

1. $\frac{2V}{3}$
2. $\frac{V}{3}$
3. $\frac{V}{2}$
4. $V$

Q. In figure, take, ${\epsilon }_1=6.0\text{V},{\epsilon }_2=1.5\text{V}$ and ${\epsilon }_3=4.5\text{V},R_1=600\Omega ,R_2=125\Omega$ and $R_3=300\Omega$. The correct option(s) is/are -

1. Current in cell ${\epsilon }_1$ is away from its positive terminal
2. Current in ${\epsilon }_2$ is is away from its negative terminal.
3. Current in ${\epsilon }_3$ is away from its negative terminal.
4. Current in ${\epsilon }_1$ is is away from its negative terminal.

Q. 12 resistors each of 10$\Omega$ are connected as shown in figure. The effective resistance between A and B is

1. 12$\Omega$
2. 10$\Omega$
3. 8$\Omega$
4. 120$\Omega$

Q. To reduce the range of voltmeter, its resistance need to be reduced. A voltmeter has resistance $R_0$ and range V. Which of the following resistances when connected in parallel will convert it into a voltmeter of range $V/n$?

1. None of these
2. $(n-1)R$
3. $n{R}_0$
4. $(n+1)R_0$

Q. When two resistors are connected in series with a cell of emf $2V$ and negligible internal resistance, a current of $2/5A$ flows in the circuit. When the resistors are connected in parallel the main current is $\frac{5}{3}A$. Calculate the resistances.

Q. A plano-convex lens (focal length ${\int }_2$ refractive index ${\mu }_2$ radius of curvature R) fits exactly into a plano-concave lens (focal length $f_1$ refractive index ${\mu }_1$ radius of curvature R). Their plane surfaces are parallel to each other. the focal of the will be :

1. $f_1-f_2$
2. $\frac{R}{{\mu }_2-{\mu }_1}$
3. $\frac{2f_1{f}_2}{f_1+f_2}$
4. $f_1+{\int }_2$

Q.
Circuit given in Fig(i) is equivalent to circuit given in Fig (ii) then

1. $E_{eq}=3V$
2. $r_{eq}=1\Omega$
3. $E_{eq}=17V$
4. Current in $1\Omega$ flow from B to A

Q. A solenoid of inductance $L$ with resistance $r$ is connected in parallel to a resistance $R$. A battery of emf $E$ and of negligible internal resistance is connected across the parallel combination as shown in the figure. At the time $t=0$, switch $S$ is opened, calculate amount of heat generated in the solenoid.

1. $\frac{E^{2}L}{\pi (R+r)}$
2. $\frac{E^{2}L}{4\pi (R+r)}$
3. $\frac{E^{2}L}{2\pi (R+r)}$
4. $\frac{{2E}^{2}L}{7\pi (R+r)}$

Q. A triode has a plate resistance of 10$k\Omega$ and amplification factor 24 . If the input signal voltage is 0.4$V(r.m.s)$ , and the load resistance is $10k\Omega ,$ then, the output voltage(r.m.s.) is

1. $4.8V$
2. $9.6V$
3. $12.0V$
4. none of these

Q. In the given electric circuit, the current flowing through $3ohm$ resistor is $1$ ampere. Find the voltage of the battery and the current drawn from it.

Q. In the circuit shown in Figure. What must the emf $ϵ$ of the battery be in order for a current of $2.00A$ to flow through the $5.00V$ battery? Is the polarity of the battery correct as shown?

Q. Three capacitors each of capacitance $9pF$ are connected in series. What is the potential difference across each capacitor if the combination is connected to a $120V$ supply?

1. $10Volt$
2. $30Volt$
3. $20Volt$
4. $40Volt$

Q. If the ammeter in the given circuit reads 2 A, the resistance R is :-

Q. An ideal ammeter A is connected as shown in the diagram. Ammeter reading is:

1. $\frac{5E}{r}$
2. $\frac{2E}{r}$
3. $\frac{E}{r}$
4. $\frac{E}{2r}$

Q. The refractive index of a material of a plano concave lens is 5/3, the radius of curvature is 0.3 m. The focal length of the lens in air is:

1. 0.45m
2. 0.6m
3. 0.75m
4. 1.0m

Q. In the circuit shown in the figure $V_1$ and $V_2$ are two voltmeters of resistance $3000\Omega$ and $2000\Omega$ respectively. $R_1=2000\Omega$ and $R_2=3000\Omega$. A is an ideal ammeter consider both cases i.e. switch S open or switch S closed to match the readings. The cell is ideal. Ammeter $\left(A_1\right)$ and $\left(A_2\right)$ are also ideal :

1. Reading of voltmeter $V_1$ in volt may be 120 Volt
2. Reading of voltmeter $V_1$ in volt may be 100 Volt
3. Reading of ammeter A may be 100 miliampere
4. Reading of ammeter $A_1$ may be 50 milliampere

Q. In the circuit shown, current flowing through $25\text{V}$ cell in amperes is: (answer the nearest integer)

Q. When the switch $S$ is closed at $t=0$, identify the correct statement just after closing the switch as shown in figure :

1. Equal and opposite voltages are dropped across inductor and resistor
2. All of the above
3. The current in the circuit is maximum
4. The entire voltage is dropped across inductor

Q.
Circuit given in Fig(i) is equivalent to circuit given in Fig (ii) then

1. $E_{eq}=3V$
2. $r_{eq}=1\Omega$
3. $E_{eq}=17V$
4. Current in $1\Omega$ flow from B to A

Q. Assertion :Current flowing in the circuit is $i=2t-8$
At $t=1s$, $V_a-V_b=+4V$ Reason: $V_a-V_b$ is $+4V$ all the time.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion is incorrect but Reason is correct

Q. The diagram shows a circuit containing a cell, an ammeter, a lamp and a variable resistor.
The resistance of the variable resistor is increased.
What happens to the ammeter reading and what happens to the brightness of the lamp?

	ammeter reading	lamp brightness
A	decreases	decreases
B	decreases	increases
C	increases	decreases
D	increases	increases

1. A
2. B
3. C
4. D