# EMF and EMF Devices

## Trending Questions

**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 π4. If instead of L, C is removed from the circuit, the phase difference between current and voltage is again π4. The power factor of the original circuit is

- 0.707
- 0.5
- 1.0
- 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 V Zener diode along with a series resistance R is connected across a 20 V supply (as shown in the figure). If the maximum Zener current is 25 mA, then the minimum value of R will be

**Q.**

Two resistors with temperature coefficients of resistance α1 and α2 have resistances R1 and R2 at 0∘C. What is the temperature coefficient of the compound resistor consisting of the two resistors connected in parallel?

α1+α22

2α1+α2α1+α2

R1α1+α2R2R1+R2

α1R2+α2R1R1+R2

**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 : 4
- 3 : 1
- 2 : 1

**Q.**

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

**Q.**A circuit connected to an ac source of emf e=e0sin(100t) with t in seconds, gives a phase difference of π4 between the emf e and current i. Which of the following circuits will exhibit this?

- RL circuit with R=1 kΩ and L=1 mH
- RL circuit with R=1 kΩ and L=10 mH
- RC circuit with R=1 kΩ and C=10 μF
- RC circuit with R=1 kΩ and C=1 μF

**Q.**

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

equal to the resistance of the load

very large as compared to the load resistance

zero

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

- Circular
- Elliptical
- Parabola
- None of these

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

- −r and ε
- r and −ε
- ε and −r
- −ε 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 :

$(13/24)L$

$(5/12)L$

$(11/24)L$

$(11/12)L$

**Q.**A potentiometer wire is 10 m long and has a resistance of 20Ω. It is connected in series with a battery of emf 3V and a resistance of 10Ω. The potential gradient along the wire in Vm−1 is

- 0.01
- 0.02
- 0.1
- 0.2

**Q.**For series RLC, circuit graph between current and frequency of voltage source is shown in figure.

Assertion:- Nature of circuit in region (1) is capacitive while in region (2) is inductive.

Reason:- Power factor of circuit in region (1) is negative and in region (2) is positive.

- Both Assertion & Reason are true & the Reason is a correct explanation of the Assertion.
- Both Assertion & Reason are true, but Reason is a correct explanation of the Assertion.
- Assertion is true, but the Reason is false.
- Both Assertion & Reason are false.

**Q.**A and 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

- repulsion between A and B, attraction between x and y.
- attraction between A and B, repulsion between x and y.
- repulsion between A and B and between x and y.
- 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 cm apart. They are connected by a 5.0 Ω resistor. The arrangement also contains two metal rods having resistances of 10.0 Ω and 15.0 Ω as shown in the figure. The rods are pulled away from the resistor at constant speeds of 4.0 m/s and 2.0 m/s respectively. A uniform magnetic field of magnitude 0.01 T is applied perpendicular to the plane of the rails. Determine the current in the 5.0 Ω resistor.

- 1.45×10−4 A
- 2.90×10−4 A
- 5.25×10−4 A
- 3.25×10−4 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 V battery connected to a 6 Ω, 10 H coil through a switch drives a constant current in the circuit. The switch is suddenly opened. Assuming that it took 1 ms to open the switch, The average emf induced across the coil is-

- 104 V
- 1.5×104 V
- 2×104 V
- 5×104 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