⚡ Master "Current and Electricity" with 100 MCQs⚡
⚡ From Basic to Expert Level! ⚡
👉Physics MCQs Hub – Unit wise Physics MCQs Practice (Main-Page)👈
Are you preparing for exams or just want to strengthen your understanding for Physics – Current & Electricity? Looking for a complete set of 100 high-quality MCQs from basic to expert level to boost your understanding and exam readiness?
This carefully curated set of Multiple Choice Questions (MCQs) covers all key topics of the unit:- Steady Current & Drift Velocity
- Ohm’s Law & Electrical Resistance
- Conductance & Resistivity
- Effect of Temperature on Resistance
- Potential Dividers & Thermistors
- Electromotive Force (EMF) & Internal Resistance
- Electric Power & Maximum Power Transfer
- Thermocouples & Resistance Thermometers
- Kirchhoff’s Laws & Wheatstone Bridge
- Potentiometer & Advanced Applications
Each question comes with a clear explanation, making it easier to understand concepts, strengthen problem-solving skills, and revise effectively before exams.
Whether you are revising for school exams, board exams, or competitive tests, this comprehensive MCQ set is designed to take your preparation to the next level.
💡 Tip: Start with the basic questions, gradually move to intermediate, and finally challenge yourself with the expert-level MCQs to maximize your learning.
Here’s what you’ll get:
- Steady Current & Drift Velocity
- Ohm’s Law & Electrical Resistance
- Conductance & Resistivity
- Effect of Temperature on Resistance
- Potential Dividers & Thermistors
- Electromotive Force (EMF) & Internal Resistance
- Electric Power & Maximum Power Transfer
- Thermocouples & Resistance Thermometers
- Kirchhoff’s Laws & Wheatstone Bridge
- Potentiometer & Advanced Applications
Set-1: Basic Level – Perfect for beginners, covering fundamentals like Steady Current, Drift Velocity, Ohm’s Law, and Electrical Resistance.
Set-2: Intermediate Level – Challenges your application skills, including Conductance, Resistivity, Effect of Temperature on Resistance, and EMF of Cells.
Set-3: Advanced Level – For deeper understanding and problem-solving, including Kirchhoff’s Laws, Wheatstone Bridge, Potentiometer, Thermistors, and Maximum Power Transfer.
Set-4: Expert Level – Tough questions that test conceptual clarity, numerical problem-solving speed, and critical thinking across all topics of Current & Electricity.
Current and Electricity MCQs (Set-1: Basic Level)
MCQ No. 1
Electric current is defined as:
a. Charge per unit area
b. Energy per unit charge
c. Charge per unit time
d. Force per unit charge
Correct answer: c. Charge per unit time
Explanation:
Electric current is the rate of flow of electric charge through a conductor.
MCQ No. 2
SI unit of electric current is:
a. Volt
b. Ohm
c. Ampere
d. Coulomb
Correct answer: c. Ampere
Explanation:
Current is measured in ampere (A), defined as coulomb per second.
MCQ No. 3
Drift velocity of electrons in a conductor depends directly on:
a. Length of wire
b. Area of wire
c. Electric field
d. Resistance
Correct answer: c. Electric field
Explanation:
Drift velocity increases with applied electric field.
MCQ No. 4
If potential difference across a conductor is doubled, current becomes:
a. Half
b. Same
c. Double
d. Four times
Correct answer: c. Double
Explanation:
According to Ohm’s law, current is directly proportional to voltage.
MCQ No. 5
Resistance of a conductor mainly depends on:
a. Current
b. Voltage
c. Length and area
d. Power
Correct answer: c. Length and area
Explanation:
Resistance increases with length and decreases with cross-sectional area.
MCQ No. 6
Which quantity remains constant for a given material at fixed temperature?
a. Resistance
b. Conductivity
c. Current
d. Voltage
Correct answer: b. Conductivity
Explanation:
Conductivity is a material property at constant temperature.
MCQ No. 7
Resistivity depends on:
a. Length
b. Area
c. Shape
d. Nature of material
Correct answer: d. Nature of material
Explanation:
Resistivity is an intrinsic property of material.
MCQ No. 8
Unit of resistivity is:
a. Ω
b. Ω m
c. Ω/m
d. S/m
Correct answer: b. Ω m
Explanation:
Resistivity is measured in ohm-meter.
MCQ No. 9
Conductance is reciprocal of:
a. Current
b. Voltage
c. Resistance
d. Power
Correct answer: c. Resistance
Explanation:
Conductance = 1/R.
MCQ No. 10
SI unit of conductance is:
a. Ohm
b. Volt
c. Siemens
d. Ampere
Correct answer: c. Siemens
Explanation:
Conductance is measured in siemens (S).
MCQ No. 11
For metallic conductors, resistance with temperature:
a. Decreases
b. Remains constant
c. Increases
d. Becomes zero
Correct answer: c. Increases
Explanation:
In metals, resistance rises due to increased lattice vibrations.
MCQ No. 12
Temperature coefficient of resistance represents:
a. Absolute resistance
b. Fractional change in resistance per degree
c. Total resistance
d. Conductivity change
Correct answer: b. Fractional change in resistance per degree
Explanation:
It shows how much resistance changes per unit temperature.
MCQ No. 13
Thermistor shows:
a. Zero temperature coefficient
b. Positive coefficient
c. Negative coefficient
d. Infinite coefficient
Correct answer: c. Negative coefficient
Explanation:
Thermistor resistance decreases as temperature increases.
MCQ No. 14
EMF of a cell is:
a. Terminal voltage
b. Energy per unit charge
c. Current × resistance
d. Power × time
Correct answer: b. Energy per unit charge
Explanation:
EMF equals work done per coulomb.
MCQ No. 15
Internal resistance exists due to:
a. External circuit
b. Electrolyte
c. Connecting wires
d. Ammeter
Correct answer: b. Electrolyte
Explanation:
Opposition inside the cell is mainly due to electrolyte.
MCQ No. 16
Unit of EMF is:
a. Ampere
b. Ohm
c. Volt
d. Watt
Correct answer: c. Volt
Explanation:
EMF is measured in volts.
MCQ No. 17
Electric power is given by:
a. I/R
b. V/I
c. VI
d. R/I
Correct answer: c. VI
Explanation:
Power equals product of voltage and current.
MCQ No. 18
If resistance doubles while voltage remains constant, power becomes:
a. Double
b. Half
c. Same
d. Four times
Correct answer: b. Half
Explanation:
P = V²/R, so power decreases when resistance increases.
MCQ No. 19
Wire-wound variable resistor is called:
a. Thermistor
b. Rheostat
c. Capacitor
d. Inductor
Correct answer: b. Rheostat
Explanation:
Rheostat controls current by changing resistance.
MCQ No. 20
Potential divider is used to obtain:
a. Constant current
b. Variable voltage
c. Maximum power
d. High resistance
Correct answer: b. Variable voltage
Explanation:
It provides adjustable output voltage.
MCQ No. 21
Thermocouple works on:
a. Joule effect
b. Seebeck effect
c. Hall effect
d. Photoelectric effect
Correct answer: b. Seebeck effect
Explanation:
Temperature difference produces EMF.
MCQ No. 22
Kirchhoff’s Current Law is based on conservation of:
a. Energy
b. Charge
c. Mass
d. Momentum
Correct answer: b. Charge
Explanation:
Total current entering a junction equals leaving.
MCQ No. 23
Kirchhoff’s Voltage Law follows conservation of:
a. Charge
b. Power
c. Energy
d. Current
Correct answer: c. Energy
Explanation:
Total energy gain equals total loss in closed loop.
MCQ No. 24
Wheatstone bridge is mainly used to find:
a. Voltage
b. Current
c. Unknown resistance
d. Power
Correct answer: c. Unknown resistance
Explanation:
Balanced bridge gives accurate resistance values.
MCQ No. 25
Potentiometer is preferred over voltmeter because it:
a. Has low resistance
b. Draws current
c. Uses null method
d. Produces power
Correct answer: c. Uses null method
Explanation:
Potentiometer measures voltage without drawing current, giving higher accuracy.
Current and Electricity MCQs (Set-2: Intermediate Level, Q26–50)
MCQ No. 26
If two resistors of 4 Ω and 6 Ω are connected in series, their equivalent resistance is:
a. 2 Ω
b. 10 Ω
c. 24 Ω
d. 1.5 Ω
Correct answer: b. 10 Ω
Explanation:
Series combination: .
MCQ No. 27
Two resistors of 4 Ω and 6 Ω are connected in parallel. The equivalent resistance is:
a. 2.4 Ω
b. 10 Ω
c. 1.5 Ω
d. 6 Ω
Correct answer: a. 2.4 Ω
Explanation:
Parallel formula: .
MCQ No. 28
Current divides in a parallel circuit according to:
a. Voltage across each resistor
b. Resistance of each branch
c. Total power
d. Total EMF
Correct answer: b. Resistance of each branch
Explanation:
Branch with smaller resistance carries higher current.
MCQ No. 29
If three equal resistors are connected in series, the total resistance is:
a. Equal to one resistor
b. Three times one resistor
c. Half of one resistor
d. Square of one resistor
Correct answer: b. Three times one resistor
Explanation:
Series: .
MCQ No. 30
If the same three resistors are connected in parallel, the total resistance is:
a. R/3
b. 3R
c. R
d. 2R
Correct answer: a. R/3
Explanation:
Parallel: .
MCQ No. 31
The drift velocity of electrons is typically of order:
a. 10 m/s
b. 10⁻³ m/s
c. 10³ m/s
d. 1 m/s
Correct answer: b. 10⁻³ m/s
Explanation:
Electrons drift slowly even under large currents.
MCQ No. 32
Maximum power is delivered to a load when:
a. Load resistance = internal resistance
b. Load resistance > internal resistance
c. Load resistance < internal resistance
d. Internal resistance = 0
Correct answer: a. Load resistance = internal resistance
Explanation:
Maximum power transfer theorem.
MCQ No. 33
In a potentiometer, null point occurs when:
a. Current is maximum
b. Potential difference across wire equals EMF
c. Wire resistance is minimum
d. Voltage across battery drops to zero
Correct answer: b. Potential difference across wire equals EMF
Explanation:
Null method avoids current in the cell.
MCQ No. 34
In a thermocouple, EMF changes with:
a. Current
b. Temperature difference
c. Resistance
d. Voltage
Correct answer: b. Temperature difference
Explanation:
Seebeck effect: EMF ∝ ΔT.
MCQ No. 35
Which of the following has highest resistance?
a. Short, thick wire
b. Long, thin wire
c. Short, thin wire
d. Long, thick wire
Correct answer: b. Long, thin wire
Explanation:
R ∝ L/A, longer length and smaller area → higher resistance.
MCQ No. 36
Internal resistance of a cell reduces:
a. Terminal voltage under load
b. EMF
c. Current in open circuit
d. Power rating
Correct answer: a. Terminal voltage under load
Explanation:
Vt = EMF – Ir; internal resistance drops voltage under current.
MCQ No. 37
Voltage across a resistor in series is:
a. Equal for all resistors
b. Proportional to its resistance
c. Proportional to current squared
d. Independent of resistance
Correct answer: b. Proportional to its resistance
Explanation:
Series: V ∝ R.
MCQ No. 38
Electrical energy consumed is measured in:
a. Watt
b. Joule
c. Watt-hour
d. Ampere
Correct answer: c. Watt-hour
Explanation:
Energy = Power × Time; units kWh or Wh.
MCQ No. 39
Resistance thermometer works on:
a. Hall effect
b. Change in resistance with temperature
c. EMF generation
d. Thermionic emission
Correct answer: b. Change in resistance with temperature
Explanation:
Platinum RTDs use resistance variation for temperature measurement.
MCQ No. 40
In Kirchhoff’s voltage law, sum of potential differences in a loop is:
a. Positive
b. Zero
c. Negative
d. Equal to EMF
Correct answer: b. Zero
Explanation:
Energy gained = Energy lost in a closed loop.
MCQ No. 41
In KCL, at any junction:
a. Sum of voltages = 0
b. Sum of currents in = Sum out
c. Product of currents = 0
d. Current is maximum
Correct answer: b. Sum of currents in = Sum out
Explanation:
Conservation of charge at junction.
MCQ No. 42
For non-ohmic conductor, current-voltage graph is:
a. Straight line
b. Curve
c. Hyperbola
d. Constant
Correct answer: b. Curve
Explanation:
Current is not directly proportional to voltage.
MCQ No. 43
A thermistor with negative temperature coefficient:
a. Increases resistance with temperature
b. Decreases resistance with temperature
c. Constant resistance
d. Infinite resistance
Correct answer: b. Decreases resistance with temperature
Explanation:
NTC thermistors have negative coefficient.
MCQ No. 44
Unit of temperature coefficient of resistivity:
a. Ω
b. Ω·m
c. K⁻¹
d. V
Correct answer: c. K⁻¹
Explanation:
Fractional change in resistivity per kelvin.
MCQ No. 45
Wheatstone bridge is balanced when:
a. All resistances are equal
b. Ratio R1/R2 = R3/R4
c. Voltage across battery is zero
d. Current is maximum
Correct answer: b. Ratio R1/R2 = R3/R4
Explanation:
Balance condition: no current through galvanometer.
MCQ No. 46
In a series circuit, total power is:
a. Sum of individual powers
b. Product of individual powers
c. Half of maximum power
d. Independent of voltage
Correct answer: a. Sum of individual powers
Explanation:
Series resistors: P_total = P1 + P2 + …
MCQ No. 47
Unit of electrical conductivity:
a. Ω⁻¹·m⁻¹
b. Ω·m
c. S·m
d. S·Ω
Correct answer: a. Ω⁻¹·m⁻¹
Explanation:
Conductivity = reciprocal of resistivity.
MCQ No. 48
If two identical cells are connected in series, total EMF is:
a. Same as one
b. Half of one
c. Double of one
d. Square of one
Correct answer: c. Double of one
Explanation:
Series EMF adds: E_total = E1 + E2.
MCQ No. 49
If two identical cells are connected in parallel, total EMF is:
a. Same as one
b. Double
c. Half
d. Zero
Correct answer: a. Same as one
Explanation:
Parallel EMF remains same, capacity (current) increases.
MCQ No. 50
For maximum power output, efficiency of circuit is:
a. 25%
b. 50%
c. 75%
d. 100%
Correct answer: b. 50%
Explanation:
At max power, load = internal resistance → efficiency = 50%.
Current and Electricity MCQs (Set-3: Advanced Level, Q51–75)
MCQ No. 51
The EMF of a cell is 12 V and internal resistance is 2 Ω. If connected to a 10 Ω resistor, current is:
a. 1 A
b. 1.2 A
c. 2 A
d. 0.5 A
Correct answer: b. 1.2 A
Explanation:
I = E / (R + r) = 12 / (10 + 2) = 1.2 A.
MCQ No. 52
A wire of length L and cross-sectional area A has resistance R. If length is doubled and area halved, new resistance is:
a. R/4
b. 4R
c. 2R
d. 8R
Correct answer: d. 8R
Explanation:
R = ρ L / A → R_new = ρ(2L)/(A/2) = 4 * 2 R = 8R.
MCQ No. 53
A conductor has negative temperature coefficient. If temperature rises, its resistance:
a. Increases
b. Decreases
c. Remains same
d. Doubles
Correct answer: b. Decreases
Explanation:
NTC conductors: resistance decreases with temperature.
MCQ No. 54
In a potentiometer, the sensitivity can be increased by:
a. Using shorter wire
b. Increasing wire resistance
c. Increasing current
d. Using thicker wire
Correct answer: b. Increasing wire resistance
Explanation:
Sensitivity ∝ potential gradient; higher resistance → higher gradient.
MCQ No. 55
In a Wheatstone bridge, galvanometer shows zero deflection. Then:
a. R1 = R2
b. Ratio R1/R2 = R3/R4
c. All resistances are equal
d. Current is maximum
Correct answer: b. Ratio R1/R2 = R3/R4
Explanation:
No current through galvanometer → balanced bridge.
MCQ No. 56
Kirchhoff’s voltage law is based on:
a. Conservation of energy
b. Conservation of charge
c. Ohm’s law
d. Maximum power theorem
Correct answer: a. Conservation of energy
Explanation:
Sum of potential differences around a loop = 0 → energy conserved.
MCQ No. 57
The unit of specific resistance (resistivity) is:
a. Ω·m
b. Ω/m
c. S·m
d. Ω⁻¹·m
Correct answer: a. Ω·m
Explanation:
ρ = R·A/L → units Ω·m.
MCQ No. 58
If the potential difference across a 5 Ω resistor is 10 V, current through it is:
a. 0.5 A
b. 2 A
c. 5 A
d. 10 A
Correct answer: b. 2 A
Explanation:
I = V / R = 10 / 5 = 2 A.
MCQ No. 59
The resistivity of a material increases with temperature if:
a. Positive temperature coefficient
b. Negative temperature coefficient
c. Constant resistance
d. Zero coefficient
Correct answer: a. Positive temperature coefficient
Explanation:
Metals generally have positive temperature coefficient.
MCQ No. 60
The EMF of a thermocouple is due to:
a. Current flow
b. Seebeck effect
c. Resistance change
d. Voltage drop
Correct answer: b. Seebeck effect
Explanation:
EMF is generated due to temperature difference.
MCQ No. 61
The power dissipated in a resistor R carrying current I is:
a. P = IR
b. P = I²R
c. P = V/I
d. P = V²/I
Correct answer: b. I²R
Explanation:
Power = current² × resistance.
MCQ No. 62
If the internal resistance of a cell is zero, the terminal voltage:
a. Is zero
b. Equals EMF
c. Less than EMF
d. Infinite
Correct answer: b. Equals EMF
Explanation:
Vt = E – Ir; r = 0 → Vt = E.
MCQ No. 63
A wire of resistivity ρ and length L has cross-section area A. Its resistance:
a. ρ A / L
b. ρ L / A
c. ρ / L
d. A / ρ L
Correct answer: b. ρ L / A
Explanation:
Basic definition of resistance.
MCQ No. 64
A potentiometer wire has uniform cross-section. The potential gradient is:
a. Constant along wire
b. Increases along wire
c. Decreases along wire
d. Zero
Correct answer: a. Constant along wire
Explanation:
Uniform wire, constant current → uniform gradient.
MCQ No. 65
Thermistors are commonly used in:
a. High-voltage circuits
b. Temperature sensors
c. Power generation
d. Magnetic field measurement
Correct answer: b. Temperature sensors
Explanation:
Resistance changes with temperature → can measure temperature.
MCQ No. 66
In series combination of resistors, the largest voltage drop occurs across:
a. Smallest resistance
b. Largest resistance
c. Middle resistance
d. All equal
Correct answer: b. Largest resistance
Explanation:
V = IR, same current → higher R → higher voltage.
MCQ No. 67
The terminal voltage of a cell is maximum when:
a. Current is maximum
b. Load resistance = internal resistance
c. No current flows (open circuit)
d. Load resistance = 0
Correct answer: c. No current flows (open circuit)
Explanation:
Vt = E – Ir; I = 0 → Vt = E.
MCQ No. 68
If a cell of EMF E and internal resistance r is short-circuited, current is:
a. Zero
b. E/r
c. E/(r + R)
d. Infinite
Correct answer: b. E/r
Explanation:
Short-circuit: external R = 0 → I = E / r.
MCQ No. 69
In a thermocouple, EMF is zero when:
a. Temperatures of junctions equal
b. Current is zero
c. Resistance is maximum
d. Voltage is maximum
Correct answer: a. Temperatures of junctions equal
Explanation:
No temperature difference → no EMF.
MCQ No. 70
Which resistor type is most suitable for high-precision circuits?
a. Carbon film
b. Wire-wound
c. Thermistor
d. NTC
Correct answer: b. Wire-wound
Explanation:
Stable, precise resistance, low temperature coefficient.
MCQ No. 71
The variation of resistivity with temperature for metals is:
a. Linear and positive
b. Linear and negative
c. Non-linear
d. Constant
Correct answer: a. Linear and positive
Explanation:
Metal resistivity increases linearly with temperature.
MCQ No. 72
An ideal voltmeter should have:
a. Zero resistance
b. Infinite resistance
c. Same as circuit resistance
d. Low resistance
Correct answer: b. Infinite resistance
Explanation:
Infinite resistance → draws negligible current → accurate measurement.
MCQ No. 73
The efficiency of a practical cell at maximum power output is:
a. 25%
b. 50%
c. 75%
d. 100%
Correct answer: b. 50%
Explanation:
Load = internal resistance → half of power lost in internal resistance.
MCQ No. 74
Kirchhoff’s laws are not applicable to:
a. DC circuits
b. AC circuits
c. Time-varying magnetic fields
d. Series resistors
Correct answer: c. Time-varying magnetic fields
Explanation:
KCL & KVL require quasi-static conditions, not valid with changing magnetic flux.
MCQ No. 75
If the resistivity of a conductor doubles, its resistance:
a. Doubles
b. Halves
c. Unchanged
d. Quadruples
Correct answer: a. Doubles
Explanation:
R ∝ ρ; doubling ρ → doubling resistance.
Current and Electricity MCQs (Set-4: Expert Level, Q76–100)
MCQ No. 76
The maximum power transfer to a load occurs when:
a. Load resistance is zero
b. Load resistance equals internal resistance of the source
c. Load resistance is infinite
d. Load resistance is double the internal resistance
Correct answer: b. Load resistance equals internal resistance of the source
Explanation:
According to maximum power theorem, maximum power is delivered when R_load = r_internal.
MCQ No. 77
For a conductor of length L and cross-section A, potential gradient is constant. If length is doubled and applied voltage is same, current:
a. Doubles
b. Halves
c. Quadruples
d. Remains same
Correct answer: b. Halves
Explanation:
Current I = V / R → R ∝ L → doubling L → R doubles → I halves.
MCQ No. 78
In a series circuit of resistances R1, R2, R3, the fraction of total voltage across R2 is:
a. R1 / (R1 + R2 + R3)
b. R2 / (R1 + R2 + R3)
c. R3 / (R1 + R2 + R3)
d. 1/3
Correct answer: b. R2 / (R1 + R2 + R3)
Explanation:
Voltage divides in proportion to resistance in series.
MCQ No. 79
The internal resistance of a cell can be determined accurately using:
a. Ammeter only
b. Voltmeter only
c. Potentiometer
d. Ohmmeter
Correct answer: c. Potentiometer
Explanation:
Potentiometer measures EMF without drawing current → accurate r calculation.
MCQ No. 80
If a wire has resistivity ρ and is stretched to double its length, its new resistance:
a. R/2
b. 2R
c. 4R
d. 8R
Correct answer: c. 4R
Explanation:
Length doubles → cross-section halves (volume constant), R ∝ L/A → R_new = 2 / (1/2) R = 4R.
MCQ No. 81
In a thermocouple, reversing the temperature difference:
a. Reverses EMF direction
b. Doubles EMF
c. Halves EMF
d. EMF remains same
Correct answer: a. Reverses EMF direction
Explanation:
Seebeck effect → EMF polarity depends on junction temperatures.
MCQ No. 82
The temperature coefficient of resistance of a material is:
a. Δρ / ρ
b. ΔR / R
c. ΔR / (R ΔT)
d. ΔV / I
Correct answer: c. ΔR / (R ΔT)
Explanation:
Defines fractional change in resistance per degree change in temperature.
MCQ No. 83
If two resistors R1 and R2 are in parallel, the current through smaller resistor is:
a. Smaller
b. Larger
c. Same
d. Zero
Correct answer: b. Larger
Explanation:
V same across both → I = V/R → smaller R → larger current.
MCQ No. 84
In a potentiometer, to measure unknown EMF accurately, the length of wire should be:
a. Very short
b. Equal to the potential difference
c. Long enough to produce measurable balance length
d. Equal to wire thickness
Correct answer: c. Long enough to produce measurable balance length
Explanation:
Longer wire → higher potential gradient → better measurement accuracy.
MCQ No. 85
In a Wheatstone bridge, if R1 = 100 Ω, R2 = 200 Ω, R3 = 150 Ω, R4 should be:
a. 150 Ω
b. 100 Ω
c. 300 Ω
d. 50 Ω
Correct answer: c. 300 Ω
Explanation:
Balanced bridge: R1/R2 = R3/R4 → 100/200 = 150/R4 → R4 = 300 Ω.
MCQ No. 86
A metallic conductor obeys Ohm’s law. If potential is doubled, current:
a. Doubles
b. Quadruples
c. Halves
d. Remains same
Correct answer: a. Doubles
Explanation:
Ohmic conductor → V ∝ I.
MCQ No. 87
If the cross-sectional area of a wire is tripled, resistance becomes:
a. 3R
b. R/3
c. R
d. 9R
Correct answer: b. R/3
Explanation:
R ∝ 1/A → area triples → resistance divided by 3.
MCQ No. 88
The EMF of a battery is 12 V and internal resistance 1 Ω. To deliver 36 W to load, load resistance should be:
a. 2 Ω
b. 4 Ω
c. 5 Ω
d. 6 Ω
Correct answer: a. 2 Ω
Explanation:
P = I² R_load, I = V / (R_load + r), solve: I² R_load = 36 → R_load = 2 Ω.
MCQ No. 89
The rate of change of thermoelectric EMF with temperature is called:
a. Seebeck coefficient
b. Peltier coefficient
c. Joule coefficient
d. Thomson coefficient
Correct answer: a. Seebeck coefficient
Explanation:
Seebeck coefficient = EMF per unit temperature difference.
MCQ No. 90
Resistance thermometers are based on:
a. Voltage drop
b. Current measurement
c. Resistance change with temperature
d. EMF generation
Correct answer: c. Resistance change with temperature
Explanation:
Platinum RTDs → resistance rises with temperature.
MCQ No. 91
If potential difference across a resistor is kept constant, and temperature rises, current:
a. Increases
b. Decreases
c. Constant
d. Doubles
Correct answer: b. Decreases
Explanation:
R increases with T → I = V/R → current decreases.
MCQ No. 92
In Kirchhoff’s current law, sum of currents entering a junction equals:
a. Zero
b. Sum of currents leaving junction
c. Resistance
d. EMF
Correct answer: b. Sum of currents leaving junction
Explanation:
Charge conservation → total inflow = total outflow.
MCQ No. 93
The internal resistance of an ideal voltage source is:
a. Zero
b. Infinity
c. One ohm
d. Varies with load
Correct answer: a. Zero
Explanation:
Ideal source → terminal voltage always equal to EMF.
MCQ No. 94
Thermistor has high sensitivity because:
a. Large positive temperature coefficient
b. Large negative temperature coefficient
c. Zero coefficient
d. Resistance independent of temperature
Correct answer: b. Large negative temperature coefficient
Explanation:
Small ΔT → large ΔR → high sensitivity.
MCQ No. 95
The potential difference across a 10 Ω resistor carrying 2 A is:
a. 5 V
b. 10 V
c. 20 V
d. 40 V
Correct answer: c. 20 V
Explanation:
V = IR = 2 × 10 = 20 V.
MCQ No. 96
A conductor has resistivity ρ at 0°C. At 100°C, resistivity is 2ρ. Temperature coefficient:
a. 0.01 /°C
b. 0.02 /°C
c. 0.1 /°C
d. 0.02 /°C
Correct answer: b. 0.01 /°C
Explanation:
ρ_T = ρ₀(1 + α ΔT) → 2ρ = ρ(1 + α × 100) → α = 0.01/°C.
MCQ No. 97
In a series circuit, total power dissipated is:
a. Sum of powers in each resistor
b. Difference of powers
c. Equal to largest resistor power
d. Independent of resistors
Correct answer: a. Sum of powers in each resistor
Explanation:
Total P = P1 + P2 + … in series.
MCQ No. 98
The law of conservation of energy in electric circuits is represented by:
a. KCL
b. KVL
c. Ohm’s law
d. Joule’s law
Correct answer: b. KVL
Explanation:
Sum of potential differences around closed loop = 0 → energy conserved.
MCQ No. 99
The resistivity of copper at 0°C is 1.7 × 10⁻⁸ Ω·m. At 100°C, resistance doubles. Its temperature coefficient:
a. 0.004 /°C
b. 0.006 /°C
c. 0.01 /°C
d. 0.02 /°C
Correct answer: c. 0.01 /°C
Explanation:
ρ_T = ρ₀(1 + α ΔT), 2 = 1 + 100 α → α = 0.01.
MCQ No. 100
The terminal voltage of a cell decreases when:
a. Load increases
b. Load decreases
c. Load resistance equals internal resistance
d. Current is zero
Correct answer: b. Load decreases
Explanation:
Vt = E – Ir → higher current (smaller R) → higher Ir drop → lower terminal voltage.
