EMF and Terminal Voltage

Q.

Name a device that helps to maintain a potential difference across a conductor.

Q.

Which of the following represents voltage? (a) Work done/(Current×Time) (b) Work done × Charge (c) (Work done×Time)/Current (d) Work done × Charge × Time

1. Work done/(Current×Time)

2. Work done × Charge

3. (Work done×Time)/Current

4. Work done × Charge × Time

Q.

Explain the meaning of the terms e.m.f., terminal voltage, and internal resistance of a cell.

Q.

The emf of a cell is always greater than its terminal voltage. Why?

Q.

Explain why is the p.d. across the terminals of a cell is more in an open circuit and reduced in a closed circuit.

Q. The device which is used to measure potential difference between two points in a circuit is called a/an ____.

1. ammeter
2. voltmeter
3. ohmmeter
4. wattmeter

Q. What is charging and dis charging of a battery how does it work

Q.

Give reasons why the terminal voltage is less than the emf of a cell.

Q. The length of a wire of a potentiometer is 100 cm and the end of its standard cell is E volt . It is employed to measure the emf of a battery whose internal resistance is 0.5 ohm. If the balance point is obtained at L=30cm from the positive end , the emf of battery is 1. 30E/100.5 2. 30E/100-0.5 30(E-0.5i)/100, where I is the current in the potentiometer wire 4. 30E/100

Q. How does a battery create a potential difference in a circuit ?

Q.

A cell supplies a current of 2A when it is connected to a $5\Omega$ resistance and supplies current of 1.2A, if it is connected to a resistance of $9\Omega$. Find the e.m.f of the cell.

1. 6V

2. 8V

3. 12V

4. 16V

Q. Maximum current produced by a cell of emf 5V and internal resistance $1\Omega$ is

1. 5 A
2. 2 A
3. 3 A
4. Zero

Q.

State two difference between the e.m.f. and terminal voltage of a cell.

Q.

A cell is used to send current to an external circuit.

(a) How does the voltage across its terminals compare with its e.m.f.?

(b) Under what condition is the e.m.f. of the cell equal to its terminal voltage?

Q.

Why voltmeter is always connected in parallel?

Q. The internal resistance of a cell is the resistance of

1. Electrolyte used in cell
2. Electrodes of the cell
3. Both (1) & (2)
4. None of these

Q. Convert the following 1) electron volt to joule 2) joule to electron volt 3) Armstrong to meters 4 ) electron volt to meters

Q.

The resistance of a cell does not depend on

1. current drawn from the cell

2. tempera of electrolyte

3. concentration of electrolytic

4. the e.m. f of the cell

Q.

In which of the following cases, the flow of electric current is maximum?

1. When the potential difference across the device is more.

2. When the potential difference across the device is less.

3. When resistance of the material used is high.

4. When there is no potential difference.

Q.

Name a device that helps to maintain potential difference across a conductor.

Q.

Potential difference across a battery is 9V. On connecting a $24\Omega$ resistor across the terminals of the battery, the voltmeter reads 7.2 V. Calculate the internal resistance of the battery.

1. $4\Omega$

2. $6\Omega$

3. $10\Omega$

4. $12\Omega$

Q. What is meant by EMF of a cell? In what unit it is expressed?
[2 MARKS]

Q. ntnttA potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4m long. When the resistance, R, connected across the given cell, has values of. (i) infinity (ii) 9.5 Ω the balancing lengths, on the potentiometer wire are found to be 3 m and 2.85 m, respectively. The value of internal resistance of the cell isnn nt ntt nttt(1) 0.25 Ω (2) 0.95 Ωnttt(3) 0.5 Ω (4) 0.75 Ωntnn ntn

Q. The conductance of a 4.5 kilo ohm resistor is .

1. $0.458m{\Omega }^{-1}$
2. $1.386m{\Omega }^{-1}$
3. $0.222m{\Omega }^{-1}$

Q. a) Define the EMF $\left(ϵ\right)$ of a cell and the potential difference (V) across a resistor R in terms of the work done in moving a unit charge.
b) State the relation between these two works and the work done in moving a unit charge through a cell connected across the resistor. Take the internal resistance of the cell of r. Hence, obtain an expression for the current (I) in the circuit.
[5 MARKS]

Q.

In the following diagram, Calculate the approximate current drawn from the cell.

1. 0.3 A

2. 0.2 A

3. 0.4 A

4. 0.1 A

5. 0.5 A

Q.

Two points have a potential difference of 10V. After connecting a conductor with zero resistance between the points, the final potential at each point becomes 25V. What could be their initial potentials?

1. 30V and 40V

2. 25V and 35V

3. 20V and 30V

4. 35V and 45V

Q. A toy train of mass 1 kg moves with a constant velocity of 8 m/s, when connected to a battery of 8 volts for 4 s. is the current in the circuit .

1. $1A$
2. $2A$
3. $3A$
4. $4A$

Q. Which of the following statements below are correct about the e.m.f of a cell:

1. It is measured by the amount of work done per unit change in moving a positive test charge in the complete circuit inside and outside the cell.
2. It depends on the amount of current drawn from the cell.
3. It is measured by the amount of work done per unit charge in moving a positive test charge in the circuit outside the cell.
4. It does not depend on the amount of current drawn from the cell.

Q. Assertion :Transformer is useful for stepping up or stepping down voltages. Reason: Transformer is a device used in D.C. circuits.

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. Both Assertion and Reason are incorrect