EMF and EMF Devices

Q.

What Is Discharge Rate Of Battery?

Q.

Assertion: In a simple battery circuit, the point of the lowest potential is the positive terminal of the battery.

Reason: The current flows towards the point of the higher potential, as it does in such a circuit from the negative to the positive terminal.

1. Both A and R are true and R is the correct explanation

2. A is true but R is false

3. Both A and R are false

4. Both A and R are true but R is not the correct explanation

Q. The example for non-ohmic resistance is

1. Copper wire
2. Carbon resistance
3. Diode
4. Tungsten wire

Q. Variation in the value of a current with time is shown in the figure below. The average value of the current in time t = 0 to t = T is

नीचे चित्र में समय के साथ धारा के मान में परिवर्तन दर्शाया गया है। समय t = 0 से t = T में धारा का औसत मान है

1. $\frac{i_0}{2}$
2. i₀
3. $\frac{i_0}{3}$
4. $\frac{i_0}{4}$

Q. A cylinder of radius $R$ and length $l$ is placed in a uniform electric field $E$ parallel to the axis of the cylinder. The total flux over the curved surface of the cylinder is

1. $\frac{E}{\pi R^2}$
2. $2\pi R^{2}E$
3. $\pi R^{2}E$
4. Zero

Q. In figure, the wires $P_1{Q}_1$ and $P_2{Q}_2$ are made to slide on the rails with same speed of $5{\text{cm s}}^{-1}.$ In this region, a magnetic field of $1\text{T}$ exists. The electric current in the $9\Omega$ resistance is

1. zero, if both wires slide towards left
2. zero, if both wires slide in opposite directions
3. $0.2\text{mA}$, if both wires move towards left
4. $0.2\text{mA},$ if both wires moves in opposite directions

Q. Potential drop across $5\Omega$ is $10V$, then EMF of the battery is

1. $12\text{V}$
2. $28\text{V}$
3. $30\text{V}$
4. $40\text{V}$

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

1. $11.7\text{V}$ and $11.8\text{V}$
2. $11.6\text{V}$ and $11.7\text{V}$
3. $11.5\text{V}$ and $11.6\text{V}$
4. $11.4\text{V}$ and $11.5\text{V}$

Q. A potentiometer wire of length $L$ and of resistance $r$ is connected in series with a battery of e.m.f. $E_0$ and a resistance $r_1$. An unknown e.m.f. $E$ is balanced at a length $l$ of the potentiometer wire. The e.m.f. $E$ will be given by

1. $\frac{E_{0}r}{(r+r_1)}\times \frac{l}{L}$
2. $\frac{E_{0}l}{L}$
3. $\frac{L{E}_{0}r}{(r+r_1)l}$
4. $\frac{L{E}_{0}r}{l{r}_1}$

Q. $10$ identical cells are connected in series with similar polarity to an external resistance. Current through this resistance is ${}^{\prime }{I}^{\prime }$. Now polarity of two cells are reversed, calculate current through same resistance.

1. $0.2I$
2. $0.4I$
3. $0.6I$
4. $0.8I$

Q. A charged particle $\left(\text{mass}m\text{and}\text{charge}q\right)$ moves along $x-\text{axis}$ with velocity $v_0$. When it passes through the origin, it enters a region having uniform electric field $E=-E\hat{j}$ which extends up to $x=d$. The equation of path of electron in the region $x>d$ is :

1. $y=\frac{qEd}{m{v}_0^2}x$
2. $y=\frac{qE{d}^2}{m{v}_0^2}x$
3. $y=\frac{qEd}{m{v}_0^2}(\frac{d}{2}-x)$
4. $y=\frac{qEd}{m{v}_0^2}(x-d)$

Q. Each capacitor shown in the figure has a capacitance of $10\mu \text{F}$. The emf of the battery is $1\text{V}$. How much charge will flow through $AB$ , if the switch $S$ is closed?

1. $\frac{10}{3}\mu \text{C}$
2. $\frac{40}{3}\mu \text{C}$
3. $\frac{20}{3}\mu \text{C}$
   
4. $20\mu \text{C}$

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

Q. EMF is a form of force.

1. True
2. False

Q. A magnetic field of $B=5t^2$ exists in a cylindrical region as shown in figure. A conducting square loop of side $l=2cm$ is placed inside a cylinder such that one of the vertex of square is at the center of cylinder.

1. EMF induced in side AB at t = 2 sec is 4 mV
2. Potential difference developed in side OA at t = 2 sec is 2 mV
3. Potential difference across side AB at t = 2 sec is 2 mV
4. EMF induced across side OA at t = 2 sec is 2mV

Q. A parallel plate capacitor of capacitance $C$ is connected to a battery and is charged to a voltage $V$. Another capacitor of capacitance $2C$ is similarly charged to a voltage $2V$. The batteries are disconnected and the capacitors are connected in parallel to each other in such a way that the positive terminal of one is connected to the negative terminal of the other capacitor. The final energy of the configuration is

1. $\frac{25C{V}^2}{6}$
2. $\frac{9C{V}^2}{2}$
3. $\frac{3C{V}^2}{2}$
4. $0$

Q. In figure, the wires $P_1{Q}_1$ and $P_2{Q}_2$ are made to slide on the rails with same speed of $5{\text{cm s}}^{-1}.$ In this region, a magnetic field of $1\text{T}$ exists. The electric current in the $9\Omega$ resistance is

1. zero, if both wires slide towards left
2. zero, if both wires slide in opposite directions
3. $0.2\text{mA}$, if both wires move towards left
4. $0.2\text{mA},$ if both wires moves in opposite directions

Q. Find the potential difference $V_P-V_Q$ between points $\text{P}$ and $\text{Q}$ as shown below.

1. $0\text{V}$
   
2. $1\text{V}$
   
3. $-4\text{V}$
   
4. $2\text{V}$
   

Q. is not an emf device.

1. Electric Generator
2. Battery
3. Solar Cell
4. Capacitor

Q. What is the internal mechanism in a cell that keeps its voltage constant?

1. Chemical reaction
2. Solar energy
3. Heat
4. Mechanical energy