Internal resistance, potential difference and emf of a cell, combinations of cells in series and parallel - Question Bank

1. Which combination of cells is generally preferred for providing a large current at low voltage?
A) Series combination
B) Parallel combination
C) Series-parallel combination
D) No specific preference
2. If two cells with EMFs E1 and E2 and internal resistances r1 and r2 are connected in parallel such that they are aiding, and E1 > E2, then the current will flow:
A) From cell 1 to cell 2
B) From cell 2 to cell 1
C) Equally from both cells
D) No current flows between cells if aiding
3. What is the unit of internal resistance?
A) Volt (V)
B) Ampere (A)
C) Ohm (Ω)
D) Watt (W)
4. A cell of EMF E and internal resistance r is connected to an external resistance R. If R is increased, what happens to the terminal voltage?
A) It increases
B) It decreases
C) It remains constant
D) It becomes equal to EMF
5. When multiple cells are connected in parallel, the equivalent internal resistance is always:
A) Greater than the smallest individual internal resistance
B) Less than the smallest individual internal resistance
C) Equal to the average of the individual internal resistances
D) Zero
6. If a battery of N identical cells in series is connected to an external resistance R, and one cell is accidentally reversed, how is the total EMF affected?
A) It remains the same
B) It increases by 2E
C) It decreases by 2E
D) It becomes zero
7. What is the primary reason a battery's voltage drops when it's nearly depleted?
A) The EMF decreases significantly.
B) The internal resistance increases significantly.
C) The external circuit resistance increases.
D) The current drawn becomes zero.
8. A cell of EMF 1.2V and internal resistance 0.5 ohm drives a current through an external resistance of 2.5 ohm. What is the power dissipated in the external resistance?
A) 0.48 W
B) 0.12 W
C) 0.60 W
D) 0.96 W
9. When cells are connected in series, the total internal resistance is the sum of individual internal resistances. This is true when:
A) They are connected in opposition
B) They are connected in the same direction
C) One is charging and the other is discharging
D) Their EMFs are equal
10. If a battery of EMF E and internal resistance r is short-circuited, what is the current?
A) E/r
B) E/(2r)
C) 0
D) Infinite
11. What happens to the internal resistance of a cell as its electrolyte ages or degrades?
A) It decreases
B) It increases
C) It remains constant
D) It becomes zero
12. Consider a circuit with two cells in parallel, E1=2V, r1=1 ohm and E2=3V, r2=1 ohm. What is the equivalent EMF?
A) 2.0V
B) 2.5V
C) 3.0V
D) 5.0V
13. If N cells are connected in parallel, and each cell has EMF E and internal resistance r, to obtain maximum current from this combination, what should be the external resistance R?
A) R = r
B) R = N*r
C) R = r/N
D) R = 0
14. A cell of EMF 2V and internal resistance 0.1 ohm is connected to an external resistance of 0.9 ohm. What is the current in the circuit?
A) 0.1 A
B) 0.2 A
C) 1 A
D) 2 A
15. What is the relationship between EMF (E), terminal voltage (V), current (I), and internal resistance (r) when a cell is discharging?
A) E = V + Ir
B) V = E + Ir
C) E = V - Ir
D) V = Ir
16. If two cells are connected in parallel, and one cell has a much larger EMF than the other, what is the likely outcome?
A) The cell with lower EMF will charge the cell with higher EMF.
B) The cell with higher EMF will discharge into the cell with lower EMF.
C) No current will flow between the cells.
D) The equivalent EMF will be the average.
17. A battery of 6 cells, each of EMF 2V and internal resistance 0.5 ohm, are connected in series. What is the total EMF and total internal resistance?
A) EMF=12V, r=3 ohm
B) EMF=2V, r=0.5 ohm
C) EMF=12V, r=0.5 ohm
D) EMF=6V, r=3 ohm
18. Two cells with EMFs 2V and 1V and internal resistances 1 ohm and 2 ohm respectively are connected in parallel. Which condition must be met for the formula E_eq = (E1r2 + E2r1) / (r1+r2) to be valid?
A) The cells must be identical
B) The cells must be connected in opposition
C) The cells must have equal internal resistances
D) The cells must be connected aiding
19. If a cell's EMF is E and its internal resistance is r, what is the maximum power that can be delivered to an external resistance?
A) E^2 / (4r)
B) E^2 / r
C) E^2 / (2r)
D) E^2 / (r/2)
20. The internal resistance of a cell is affected by which of the following factors?
A) The area of electrodes
B) The distance between electrodes
C) The nature and concentration of the electrolyte
D) All of the above
21. When is the potential difference across the terminals of a cell equal to its EMF?
A) When the cell is discharging
B) When the cell is charging
C) When no current is drawn from the cell (open circuit)
D) When connected to a very low external resistance
22. A battery consists of 10 cells, each of EMF 1.5V and internal resistance 0.2 ohm, connected in series. If this battery is connected to an external resistance of 3 ohm, what is the current?
A) 1.5A
B) 3A
C) 0.5A
D) 0.75A
23. Four identical cells, each of EMF 1.5V and internal resistance 0.5 ohm, are connected in parallel. What is the equivalent EMF and internal resistance?
A) EMF=1.5V, r=2 ohm
B) EMF=6V, r=0.125 ohm
C) EMF=1.5V, r=0.125 ohm
D) EMF=6V, r=2 ohm
24. Two cells, 2V/0.5 ohm and 3V/1 ohm, are connected in series aiding. What is the total EMF and total internal resistance?
A) EMF=5V, r=1.5 ohm
B) EMF=1V, r=0.5 ohm
C) EMF=5V, r=0.5 ohm
D) EMF=1V, r=1.5 ohm
25. A cell of EMF 1.5V and internal resistance 1 ohm is connected to an external resistance of 2 ohms. What is the terminal voltage?
A) 0.5V
B) 1.0V
C) 1.5V
D) 2.0V
26. In a parallel combination of cells, if the cells have unequal EMFs but equal internal resistances, what is the equivalent EMF?
A) The average of the EMFs
B) The EMF of the cell with the highest EMF
C) The EMF of the cell with the lowest EMF
D) It cannot be determined
27. In a series combination of cells, if one cell is reversed, how does it affect the total EMF?
A) It increases
B) It decreases
C) It remains the same
D) It becomes zero
28. The internal resistance of a cell can be determined experimentally using a voltmeter and an ammeter. If the terminal voltage is V when current I is drawn, and the EMF is E when no current is drawn, what is the internal resistance?
A) (E - V) / I
B) (V - E) / I
C) E / I
D) V / I
29. What is the power dissipated internally in the cell when a cell of EMF E and internal resistance r is connected to an external resistance R?
A) E^2 * R / (R + r)^2
B) E^2 * r / (R + r)^2
C) E^2 / R
D) E^2 / r
30. What is the power dissipated in the external resistance R when a cell of EMF E and internal resistance r is connected to it?
A) E^2 * R / (R + r)^2
B) E^2 * r / (R + r)^2
C) E^2 / R
D) E^2 / r
31. What is the condition for maximum current when a battery of EMF E and internal resistance r is connected to an external resistance R?
A) R << r
B) R >> r
C) R = r
D) R = 0
32. If 'n' identical cells, each of EMF E and internal resistance r, are connected in parallel, what is the total internal resistance?
A) r
B) nr
C) r/n
D) 0
33. If 'n' identical cells, each of EMF E and internal resistance r, are connected in parallel, what is the total EMF?
A) E
B) nE
C) E/n
D) 0
34. If 'n' identical cells, each of EMF E and internal resistance r, are connected in series, what is the total internal resistance?
A) r
B) nr
C) r/n
D) 0
35. If 'n' identical cells, each of EMF E and internal resistance r, are connected in series, what is the total EMF?
A) E
B) nE
C) E/n
D) 0
36. For parallel combination of cells to be most effective in providing current, their EMFs should be:
A) As different as possible
B) Equal
C) Zero
D) Negative
37. If two cells with EMFs E1, E2 and internal resistances r1, r2 are connected in parallel, what is the equivalent internal resistance (r_eq)?
A) (r1 + r2) / (r1 * r2)
B) (r1 * r2) / (r1 + r2)
C) r1 + r2
D) (r1 + r2) / 2
38. If two cells with EMFs E1, E2 and internal resistances r1, r2 are connected in parallel, what is the equivalent EMF (E_eq)?
A) (E1*r2 + E2*r1) / (r1 + r2)
B) (E1*r1 + E2*r2) / (r1 + r2)
C) (E1 + E2) / 2
D) (E1*r2 + E2*r1) / (r2 + r1)
39. If two cells are connected in series in opposition, what is the resultant EMF?
A) E1 + E2
B) E1 * E2
C) E1 - E2 (assuming E1 > E2)
D) E2 - E1 (assuming E1 > E2)
40. When cells are connected in series, the total EMF is the algebraic sum of individual EMFs. This is true when:
A) They are connected in opposition
B) They are connected in the same direction
C) One is charging and the other is discharging
D) Their internal resistances are equal
41. If two cells with EMFs E1, E2 and internal resistances r1, r2 are connected in series, what is the total internal resistance?
A) r1 / r2
B) r1 - r2
C) r1 + r2
D) r1 * r2
42. If two cells with EMFs E1, E2 and internal resistances r1, r2 are connected in series, what is the total EMF?
A) E1 - E2
B) E1 * E2
C) E1 + E2
D) E1 / E2
43. What happens to the terminal voltage of a cell when it is discharging and the external resistance decreases?
A) Increases
B) Decreases
C) Remains constant
D) Becomes zero
44. If a cell of EMF E and internal resistance r is connected to an external resistance R, what is the current flowing through the circuit?
A) E / (R - r)
B) E / r
C) E / (R + r)
D) R / E
45. When a cell is discharging, the terminal voltage is related to EMF and internal resistance by which formula?
A) V = E + Ir
B) V = E
C) V = E - Ir
D) V = Ir
46. When a cell is being charged, the terminal voltage is related to EMF and internal resistance by which formula?
A) V = E - Ir
B) V = E + Ir
C) V = Ir
D) V = E
47. For an ideal cell, what is its internal resistance?
A) Infinite
B) Very high
C) Zero
D) Equal to external resistance
48. What is the potential difference across the terminals of a source called when current is being drawn from it?
A) Electromotive Force (EMF)
B) Internal Resistance
C) Terminal Voltage
D) Open Circuit Voltage
49. Which quantity represents the total energy supplied by a source per unit charge when no current is drawn from it?
A) Internal Resistance
B) Potential Difference
C) Terminal Voltage
D) Electromotive Force (EMF)
50. What is defined as the opposition to the flow of current within the source of electromotive force itself?
A) Electromotive Force (EMF)
B) Potential Difference
C) Internal Resistance
D) Terminal Voltage
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