EMF and EMF Devices

Q. A series $LCR$ circuit is connected to an ac voltage source. When $L$ is removed from circuit, the phase difference between current and voltage is $\frac{\pi }{4}$. If instead of $L,C$ is removed from the circuit, the phase difference between current and voltage is again $\frac{\pi }{4}$. The power factor of the original circuit is

1. $0.707$
2. $0.5$
3. $1.0$
4. $0.785$

Q.

How do capacitors behave in DC and AC circuit?

Q.

What is the difference between electrochemical cell and electrolytic cell?

Q. A $8\text{V}$ Zener diode along with a series resistance $R$ is connected across a $20\text{V}$ supply (as shown in the figure). If the maximum Zener current is $25\text{mA}$, then the minimum value of $R$ will be $\omega$

Q.

Two resistors with temperature coefficients of resistance ${\alpha }_1$ and ${\alpha }_2$ have resistances $R_1$ and $R_2$ at $0^{\circ }C$. What is the temperature coefficient of the compound resistor consisting of the two resistors connected in parallel?

1. $\frac{{\alpha }_1+{\alpha }_2}{2}$

2. $\frac{2{\alpha }_1+{\alpha }_2}{{\alpha }_1+{\alpha }_2}$

3. $\frac{R_1{\alpha }_1+{\alpha }_2{R}_2}{R_1+R_2}$

4. $\frac{{\alpha }_1{R}_2+{\alpha }_2{R}_1}{R_1+R_2}$

Q. A potentiometer has a uniform potential gradient across it. Two cells connected in series - (i) to support each other and (ii) to oppose each other are balanced over 6 m and 2 m respectively on the potentiometer wire. The emfs of the cells are in the ratio

1. 1 : 1
2. 1 : 4
3. 3 : 1
4. 2 : 1

Q.

Calculate the charge carried by 12.5*10raised to power 8 electrons

Q. A circuit connected to an $ac$ source of $\text{emf}e=e_0\sin \left(100t\right)$ with $t$ in $\text{seconds}$, gives a phase difference of $\frac{\pi }{4}$ between the $\text{emf}e$ and current $i$. Which of the following circuits will exhibit this?

1. RL circuit with $R=1\text{k}\Omega$ and $L=1\text{mH}$
2. RL circuit with $R=1\text{k}\Omega$ and $L=10\text{mH}$
3. RC circuit with $R=1\text{k}\Omega$ and $C=10\mu \text{F}$
4. RC circuit with $R=1\text{k}\Omega$ and $C=1\mu \text{F}$

Q.

An energy source will supply a constant current into the load if its internal resistance is?

1. equal to the resistance of the load

2. very large as compared to the load resistance

3. zero

4. Non-zero but less than the resistance of the load

Q. An electron is moving towards x-axis. An electric field is along y-direction then path of electron is

1. Circular
2. Elliptical
3. Parabola
4. None of these

Q. A student measures the terminal potential difference $\left(V\right)$ of a cell (of emf $\epsilon$ and internal resistance $r$) as a function of the current $\left(I\right)$ flowing through it. The slope and intercept of the graph between $V$ and $I$ are respectively equal to

1. $-r$ and $\epsilon$
2. $r$ and $-\epsilon$
3. $\epsilon$ and $-r$
4. $-\epsilon$ and $r$

Q.

Write two differences between emf and potential difference.

Q.

The frequency of the direct current is?

Q. If the Value of resistance is 10.845ohm and the value of current is 3.23 Amp, the value of potential with significant numbers would be

Q.

A potentiometer wire $AB$ having length $L$ and resistance $12r$ is joined to a cell $D$ of emf $\epsilon$ and internal resistance $3r$ is connected. The length $AJ$ at which the galvanometer as shown in fig. shows no deflection is :

1. $(13/24)L$

2. $(5/12)L$

3. $(11/24)L$

4. $(11/12)L$

Q. A potentiometer wire is 10 m long and has a resistance of $20\Omega$. It is connected in series with a battery of emf 3V and a resistance of $10\Omega$. The potential gradient along the wire in $V{m}^{-1}$ is

1. 0.01
2. 0.02
3. 0.1
4. 0.2

Q. For series $\text{RLC}$, circuit graph between current and frequency of voltage source is shown in figure.

$\text{Assertion}:$- Nature of circuit in region $\left(1\right)$ is capacitive while in region $\left(2\right)$ is inductive.

$\text{Reason}:$- Power factor of circuit in region $\left(1\right)$ is negative and in region $\left(2\right)$ is positive.

1. Both $\text{Assertion}$ & $\text{Reason}$ are true & the $\text{Reason}$ is a correct explanation of the $\text{Assertion}$.
2. Both $\text{Assertion}$ & $\text{Reason}$ are true, but $\text{Reason}$ is a correct explanation of the $\text{Assertion}$.
3. $\text{Assertion}$ is true, but the $\text{Reason}$ is false.
4. Both $\text{Assertion}$ & $\text{Reason}$ are false.

Q. $\text{A}$ and $\text{B}$ are two conductors carrying a current $i$ in the same direction. $x$ and $y$ are two electron beams moving in the same direction. There will be

1. repulsion between $A$ and $B$, attraction between $x$ and $y$.
2. attraction between $A$ and $B$, repulsion between $x$ and $y$.
3. repulsion between $A$ and $B$ and between $x$ and $y$.
4. attraction between $A$ and $B$ and between $x$ and $y$.

Q.

Does higher Ohms mean more Resistance?

Q.

What happens when a battery is disconnected from a capacitor?

Q. Two parallel rails with negligible resistance are $10.0\text{cm}$ apart. They are connected by a $5.0\Omega$ resistor. The arrangement also contains two metal rods having resistances of $10.0\Omega$ and $15.0\Omega$ as shown in the figure. The rods are pulled away from the resistor at constant speeds of $4.0\text{m/s}$ and $2.0\text{m/s}$ respectively. A uniform magnetic field of magnitude $0.01\text{T}$ is applied perpendicular to the plane of the rails. Determine the current in the $5.0\Omega$ resistor.

1. $1.45\times {10}^{-4}\text{A}$
2. $2.90\times {10}^{-4}\text{A}$
3. $5.25\times {10}^{-4}\text{A}$
4. $3.25\times {10}^{-4}\text{A}$

Q.

What happen when capacitor is connected to a battery?

Q. In a network as shown in the figure the potential difference across 2R is ( the cell has emf E volt and has no resistance) 1 2E 2 4E/7 3 E/7 4 E

Q. A $12\text{V}$ battery connected to a $6\Omega$, $10\text{H}$ coil through a switch drives a constant current in the circuit. The switch is suddenly opened. Assuming that it took $1\text{ms}$ to open the switch, The average emf induced across the coil is-

1. ${10}^4\text{V}$
2. $1.5\times {10}^4\text{V}$
3. $2\times {10}^4\text{V}$
4. $5\times {10}^4\text{V}$

Q. What are the advantages of using AC over DC?

Q.

If force f length L current I and time t are taken as the basic quantities find the dimension of E_o.

Q. Induced electric field due to change in magnetic field.

Q.

A wire of 15ohm is gradually stretched to twice it's original length it is then cut into two equal parts these parts are then connected in parallel a cross 3volt battery find current drawn from battery

Q. Describe briefly, with the help of a circuit diagram, how a potentiometer is used to determine the internal resistance of a cell.

Q. 39. Two fixed charges A and B of 5 micro coulomb each are separated by a distance of 6m.C is the mid point of the line joining A and B. A charge Q of -5micro coulomb is shot perpendicular to the line joining A and B through C with a kinetic energy of 0.06J . The charge Qcomes to rest at point D, then CD is