Under what condition is the terminal potential difference of a cell equal to its emf?
Correct answer D. When no current is drawn from the cell
Topic / 30 questions
Current Electricity MCQs
Current Electricity MCQs cover steady current, Ohm's law, resistivity and its temperature dependence, internal resistance of cells and the condition for maximum power transfer. They help MDCAT, ECAT and FSc candidates revise circuit concepts and calculations, and every question on MCQs360 shows its correct answer instantly so you can check yourself.
- Electromagnetic Induction 30
- Fluid Dynamics 30
- Electrostatics 30
- Electronics 30
- Electromagnetism 30
- Current Electricity 30
- Work and Energy 30
- Waves 30
- Vectors and Equilibrium 30
- Nuclear Physics 30
- Dawn of Modern Physics 30
- Thermodynamics 30
- Rotational and Circular Motion 30
- Atomic Spectra 30
- Alternating Current 30
- Force and Motion 30
Why must a car battery have a very low internal resistance?
Correct answer A. So it can supply a large starting current without a large drop in terminal voltage
Which change would increase the internal resistance of a simple electrolytic cell?
Correct answer A. Increasing the separation between its electrodes
Advertisement
Two identical cells, each of emf 1.5 V and internal resistance 0.50 Ω, are connected in series with a 2.0 Ω resistor. What current flows?
Correct answer C. 1.0 A
For an ohmic conductor at constant temperature, what does a graph of current against potential difference look like?
Correct answer C. A straight line through the origin with gradient 1/R
A 20 Ω resistor carries a steady current of 0.30 A. What power is dissipated in it?
Correct answer D. 1.8 W
In which direction does conventional current flow in the external part of a circuit connected to a cell?
Correct answer C. From the positive terminal to the negative terminal
A load resistor connected to a cell is increased from a value equal to the internal resistance to a much larger value. What happens to the efficiency of power transfer?
Correct answer C. It increases towards 100%
When a source delivers maximum power to its external load, what is the efficiency of power transfer?
Correct answer A. 50%
Advertisement
A source has emf 12 V and internal resistance 2.0 Ω. What is the maximum power it can deliver to an external resistor?
Correct answer D. 18 W
For a source of fixed emf and internal resistance r, the power delivered to an external load R is maximum when ____.
Correct answer B. R = r
A cell has emf 1.5 V and internal resistance 0.25 Ω. What current flows if its terminals are joined by a wire of negligible resistance?
Correct answer A. 6.0 A
What is the current when a cell of emf E and internal resistance r is short-circuited by a thick copper wire of negligible resistance?
Correct answer D. E/r
A battery of emf 9.0 V has a terminal potential difference of 7.5 V when it delivers 1.5 A. What is its internal resistance?
Correct answer C. 1.0 Ω
A battery of emf 12 V and internal resistance 0.50 Ω is connected to a 5.5 Ω resistor. What is the potential difference across the battery terminals?
Correct answer A. 11 V
Advertisement
When a cell supplies current to an external resistor, how does its terminal potential difference compare with its emf?
Correct answer B. It is less than the emf because of the voltage drop across the internal resistance
Which statement correctly describes a superconductor?
Correct answer A. Its resistance becomes zero below a critical temperature
What is the SI unit of the temperature coefficient of resistance?
Correct answer A. K⁻¹
A metal coil has resistance 20 Ω at 20 °C and 24 Ω at 120 °C. Taking 20 °C as the reference, what is its temperature coefficient of resistance?
Correct answer C. 2.0 × 10⁻³ K⁻¹
Ohm’s law states that the current in a metallic conductor is directly proportional to the potential difference across it, provided which quantity stays constant?
Correct answer D. Temperature of the conductor
About Current Electricity MCQs
Questions begin with electric current as the rate of flow of charge, including finding how many electrons pass a point each second. Ohm's law questions ask about the I-V graph of an ohmic conductor and simple circuit calculations. Resistivity questions test what it depends on, the temperature coefficient of resistance and its unit, and the behaviour of superconductors. The unit also covers emf, internal resistance and terminal voltage for single cells and cells in series, and the condition under which a source delivers maximum power to its load, along with the efficiency at that point.
Key facts to remember
- Current I = Q/t = nAve; one ampere is one coulomb per second.
- Ohm's law: V = IR for an ohmic conductor at constant temperature, so its I-V graph is a straight line through the origin.
- Resistance R = ρL/A; resistivity ρ depends on the material and temperature, not on the conductor's length or area.
- Temperature dependence: R_T = R₀(1 + αΔT), where α is measured in K⁻¹.
- Terminal voltage V = ε − Ir, where r is the internal resistance of the source.
- Maximum power is delivered to a load when R = r, giving P_max = ε²/4r at 50% efficiency.
Exams that include Current Electricity MCQs
Pakistan
- MDCAT
- ECAT (UET)
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Current Electricity MCQs
- Use n = I/e to find how many electrons pass per second, keeping milliamperes converted to amperes.
- For cells in series, add emfs and internal resistances before applying I = ε/(R + r).
- Remember that maximum power transfer and maximum efficiency are not the same: efficiency is only 50% at maximum power.
- Separate resistance (depends on shape) from resistivity (property of the material) when reading options.
Frequently asked questions
Which exams ask Current Electricity MCQs?
Current Electricity is part of the FSc physics syllabus, so its MCQs appear in MDCAT, ECAT (UET), NUMS and AKU entry tests and in FSc board papers. Students in India meet the same ideas in NEET and JEE Main, and Bangladeshi students in HSC and the medical admission test.
What is the condition for maximum power transfer?
A source delivers maximum power to an external load when the load resistance equals the internal resistance of the source, R = r. At this point the power is ε²/4r, and the efficiency is 50% because equal power is wasted inside the source.
Last reviewed October 2026