Current & Electricity – 100 Basic MCQs with Answers & Explanations | Board & MDCAT Preparation

100 Important Basic MCQs (Level -1) on Current & Electricity, Physics (Unit-Wise MCQs Practice):

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👉Physics MCQs Hub – Unit wise Physics MCQs Practice (Main-Page)👈

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Whether you are preparing for board examinations, chapter tests, college assessments, or competitive entrance exams (MDCAT, ECAT, NUST, PIEAS, GIKI, UET, FAST, and other engineering or medical admission tests), this comprehensive MCQ collection is designed to help you master Current & Electricity. The questions are arranged progressively—from basic concepts to advanced numerical problems and higher-order thinking—ensuring complete and systematic preparation for every type of examination.

This chapter-wise MCQ collection includes:

• 100 Basic MCQs (1–100) – Covering steady current, drift velocity, Ohm's law, resistance, resistivity, conductivity, EMF, electric power, and related fundamental concepts.
• 100 Advanced & Numerical MCQs (101–200) – Focusing on calculations, circuit analysis, Kirchhoff's laws, Wheatstone bridge, potentiometer, thermistors, internal resistance, and power applications.
• 50 Higher-Order Thinking Skills (HOTS) MCQs (201–250) – Designed to develop conceptual understanding, analytical reasoning, and advanced problem-solving skills.
• 50 Challenging MCQs Quiz-1 with Answers (1–50) and 50 Challenging MCQs Quiz-2 with Answers (1–50) – A carefully selected mix of conceptual, numerical, and HOTS questions for quick revision, self-assessment, and complete exam preparation.

This MCQ collection covers:

• Steady current and drift velocity
• Ohm's law and electrical resistance
• Resistivity, conductivity, and conductance
• Temperature effects on resistance and resistivity
• Variable resistors, thermistors, and potential divider
• Electromotive force (EMF) and internal resistance
• Electric power and maximum power transfer
• Thermocouples and resistance thermometers
• Kirchhoff's Current Law (KCL) and Voltage Law (KVL)
• Wheatstone bridge and potentiometer

Every MCQ includes the correct answer with a clear, concept-based explanation to strengthen understanding, improve numerical ability, and reinforce key physics concepts.

This question bank helps students to:

• Build strong conceptual understanding
• Improve numerical and analytical skills
• Master electrical circuits and network analysis
• Strengthen problem-solving techniques
• Avoid common examination mistakes
• Increase speed, accuracy, and confidence
• Prepare effectively for both board and competitive examinations

With 250 carefully selected MCQs arranged into 100 Basic, 100 Advanced & Numerical, and 50 HOTS questions, along with 50 Challenging Quiz MCQs, this all-in-one Current & Electricity MCQ Bank provides complete preparation for examinations and competitive entrance tests while helping students achieve maximum scores.

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Current & Electricity (Level 1) – 100 Basic MCQs with Answers & Explanations (1 - 100)

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MCQ No. 1

The value of current in an open circuit is:

a. Zero
b. Infinite
c. Maximum
d. Very small

Correct answer: a. Zero

Explanation:
An open circuit has infinite resistance. According to Ohm's law, $I=\frac{V}{R}$ . Since $R \rightarrow \infty$ , the current becomes zero.

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MCQ No. 2

The drift velocity of free electrons in a metallic conductor is typically of the order of:

a. $10^{-6}\,\text{m/s}$
b. $10^{-3}\,\text{m/s}$
c. $10^{3}\,\text{m/s}$
d. $10^{6}\,\text{m/s}$

Correct answer: b. $10^{-3}\,\text{m/s}$

Explanation:
Although electrons move randomly at very high speeds, their average drift velocity under an electric field is extremely small, approximately $10^{-3}\,\text{m/s}$.

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MCQ No. 3

Current in an electrolyte is carried by:

a. Electrons only
b. Positive ions only
c. Positive and negative ions
d. Protons only

Correct answer: c. Positive and negative ions

Explanation:
In electrolytes, electric current is produced by the movement of both positive ions (cations) and negative ions (anions).

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MCQ No. 4

The SI unit of conductance is:

a. Ohm (Ω)
b. Siemens (S)
c. Ohm-metre (Ω m)
d. Mho m⁻¹

Correct answer: b. Siemens (S)

Explanation:
Conductance is the reciprocal of resistance. Its SI unit is the siemens (S).

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MCQ No. 5

The reciprocal of resistance is called:

a. Resistivity
b. Conductivity
c. Conductance
d. Conductance coefficient

Correct answer: c. Conductance

Explanation:
Conductance is defined as $G=\frac{1}{R}$, where $R$  is the resistance.

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MCQ No. 6

The SI unit of resistivity is:

a. Ω
b. Ω m
c. Ω m⁻¹
d. S m⁻¹

Correct answer: b. Ω m

Explanation:
Resistivity is a material property. Its SI unit is ohm-metre (Ω m).

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MCQ No. 7

According to Ohm's law, the current through a conductor is directly proportional to:

a. Resistance
b. Length of the conductor
c. Potential difference across it
d. Resistivity

Correct answer: c. Potential difference across it

Explanation:
Ohm's law states that $I \propto V$ , provided the temperature and other physical conditions remain constant.

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MCQ No. 8

Resistance of a conductor depends upon:

a. Length only
b. Cross-sectional area only
c. Nature of material only
d. Length, cross-sectional area, and material

Correct answer: d. Length, cross-sectional area, and material

Explanation:
Resistance is given by $R=\rho \frac{L}{A}$. Therefore, it depends on resistivity, length, and cross-sectional area.

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MCQ No. 9

When a wire is cut into two equal parts, the resistance of each part becomes:

a. Double
b. Half
c. Four times
d. Unchanged

Correct answer: b. Half

Explanation:
Since resistance is directly proportional to length, halving the length halves the resistance.

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MCQ No. 10

The resistivity of a material depends mainly upon:

a. Its dimensions
b. Its mass
c. Its material and temperature
d. Its shape

Correct answer: c. Its material and temperature

Explanation:
Resistivity is an intrinsic property of a material and changes mainly with temperature.

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MCQ No. 11

For an open circuit, the terminal potential difference of a cell is:

a. Greater than its emf
b. Equal to its emf
c. Less than its emf
d. Zero

Correct answer: b. Equal to its emf

Explanation:
When no current flows, there is no voltage drop across the internal resistance, so terminal voltage equals the emf.

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MCQ No. 12

For a cell supplying current to a circuit:

a. EMF is less than terminal voltage.
b. EMF is equal to terminal voltage.
c. EMF is greater than terminal voltage.
d. Terminal voltage is always zero.

Correct answer: c. EMF is greater than terminal voltage.

Explanation:
Some potential is lost across the internal resistance of the cell; therefore, the terminal voltage is less than the emf.

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MCQ No. 13

Kirchhoff's Current Law (KCL) is based on the law of conservation of:

a. Energy
b. Momentum
c. Charge
d. Mass

Correct answer: c. Charge

Explanation:
The algebraic sum of currents entering and leaving a junction is zero because electric charge is conserved.

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MCQ No. 14

Kirchhoff's Voltage Law (KVL) is based on the law of conservation of:

a. Charge
b. Mass
c. Energy
d. Momentum

Correct answer: c. Energy

Explanation:
The algebraic sum of all potential differences around any closed loop is zero, which follows from the conservation of energy.

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MCQ No. 15

The SI unit of conductivity is:

a. Ω m
b. Siemens (S)
c. S m⁻¹
d. Ω⁻¹

Correct answer: c. S m⁻¹

Explanation:
Conductivity is the reciprocal of resistivity. Its SI unit is siemens per metre (S m⁻¹).

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MCQ No. 16

An ideal voltmeter should have:

a. Zero resistance
b. Infinite resistance
c. Low resistance
d. One ohm resistance

Correct answer: b. Infinite resistance

Explanation:
An ideal voltmeter draws no current from the circuit, so it must have infinite resistance.

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MCQ No. 17

The instrument used to compare the e.m.f. of two cells accurately is:

a. Ammeter
b. Voltmeter
c. Potentiometer
d. Galvanometer

Correct answer: c. Potentiometer

Explanation:
A potentiometer compares e.m.f.s without drawing current from the cells, making it highly accurate.

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MCQ No. 18

An ideal current source has:

a. Zero internal resistance
b. Infinite internal resistance
c. Very low emf
d. Zero emf

Correct answer: b. Infinite internal resistance

Explanation:
An ideal current source maintains constant current regardless of load; therefore, it has infinite internal resistance.

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MCQ No. 19

A wire is stretched to twice its original length without changing its volume. Its resistance becomes:

a. Twice the original value
b. Three times the original value
c. Four times the original value
d. Eight times the original value

Correct answer: c. Four times the original value

Explanation:
When the length doubles, the cross-sectional area becomes half (volume remains constant). Thus,
$R'=\rho \frac{2L}{A/2}=4R$

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MCQ No. 20

The SI unit of electric current is:

a. Coulomb
b. Volt
c. Ampere
d. Ohm

Correct answer: c. Ampere

Explanation:
The ampere (A) is the SI unit of electric current.

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MCQ No. 21

If 5 A of current flows for 2 minutes, the charge transferred is:

a. 300 C
b. 500 C
c. 600 C
d. 1200 C

Correct answer: c. 600 C

Explanation:
Using $Q=It$:

$$Q=5\times120=600\ \text{C}$$

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MCQ No. 22

The SI unit of electromotive force (e.m.f.) is:

a. Ampere
b. Coulomb
c. Volt
d. Watt

Correct answer: c. Volt

Explanation:
Electromotive force is a potential difference and is measured in volts (V).

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MCQ No. 23

A 100 Ω resistor connected across a 220 V supply draws a current of:

a. 0.22 A
b. 2.2 A
c. 22 A
d. 220 A

Correct answer: b. 2.2 A

Explanation:
According to Ohm's law,

$$I=\frac{V}{R}=\frac{220}{100}=2.2\ \text{A}$$

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MCQ No. 24

Which instrument is primarily used to vary the current in an electric circuit?

a. Potentiometer
b. Rheostat
c. Galvanometer
d. Transformer

Correct answer: b. Rheostat

Explanation:
A rheostat is a variable resistor used to control the current flowing through a circuit.

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MCQ No. 25

The temperature coefficient of resistance for pure metallic conductors is generally:

a. Negative
b. Zero
c. Positive
d. Infinite

Correct answer: c. Positive

Explanation:
For metallic conductors, resistance increases with temperature; therefore, they have a positive temperature coefficient of resistance.

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MCQ No. 26

The SI unit of electric current is:

a. Volt
b. Ampere
c. Coulomb
d. Ohm

Correct answer: b. Ampere

Explanation:
The SI unit of electric current is the ampere (A), which is equal to one coulomb of charge flowing per second.

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MCQ No. 27

The resistance of a conductor depends upon:

a. Length only
b. Area only
c. Material only
d. Length, area, and material

Correct answer: d. Length, area, and material

Explanation:
Resistance depends on the conductor's length, cross-sectional area, and the resistivity of its material.

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MCQ No. 28

The reciprocal of resistivity is called:

a. Resistance
b. Conductance
c. Conductivity
d. Current density

Correct answer: c. Conductivity

Explanation:
Conductivity (σ) is the reciprocal of resistivity (ρ), i.e., σ = 1/ρ.

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MCQ No. 29

The current in a metallic conductor is due to the motion of:

a. Positive ions
b. Electrons
c. Protons
d. Neutrons

Correct answer: b. Electrons

Explanation:
In metals, electric current is produced by the movement of free electrons.

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MCQ No. 30

The relation between charge, current, and time is:

a. I = qt
b. I = q/t
c. q = I/t
d. t = qI

Correct answer: b. I = q/t

Explanation:
Current is the rate of flow of electric charge.

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MCQ No. 31

A resistor having a larger cross-sectional area possesses:

a. Higher resistance
b. Lower resistance
c. Infinite resistance
d. Zero resistance

Correct answer: b. Lower resistance

Explanation:
Resistance is inversely proportional to cross-sectional area.

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MCQ No. 32

The current through a resistor is doubled while its resistance remains constant. The potential difference becomes:

a. Half
b. Double
c. Four times
d. Unchanged

Correct answer: b. Double

Explanation:
From Ohm's law, V = IR. If current doubles, voltage also doubles.

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MCQ No. 33

The SI unit of conductance is:

a. Ohm
b. Siemens
c. Volt
d. Watt

Correct answer: b. Siemens

Explanation:
Conductance is measured in siemens (S).

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MCQ No. 34

In metallic conductors, increasing temperature generally causes:

a. Increase in conductivity
b. Decrease in resistance
c. Increase in resistance
d. No change in resistance

Correct answer: c. Increase in resistance

Explanation:
Higher temperature increases atomic vibrations, causing greater resistance.

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MCQ No. 35

A wire is stretched to twice its original length. Its resistance becomes:

a. Same
b. Double
c. Four times
d. Half

Correct answer: c. Four times

Explanation:
When stretched to double length, its area becomes half, making resistance four times larger.

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MCQ No. 36

Current density is defined as current flowing per unit:

a. Length
b. Volume
c. Cross-sectional area
d. Resistance

Correct answer: c. Cross-sectional area

Explanation:
Current density J = I/A.

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MCQ No. 37

The commercial unit of electrical energy is:

a. Joule
b. Watt
c. Kilowatt-hour
d. Ampere-hour

Correct answer: c. Kilowatt-hour

Explanation:
Electrical energy consumed commercially is measured in kilowatt-hour (kWh).

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MCQ No. 38

Which quantity remains constant in a series circuit?

a. Voltage
b. Power
c. Current
d. Resistance

Correct answer: c. Current

Explanation:
The same current flows through every component connected in series.

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MCQ No. 39

The SI unit of electromotive force (e.m.f.) is:

a. Ampere
b. Joule
c. Volt
d. Watt

Correct answer: c. Volt

Explanation:
Electromotive force is measured in volts.

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MCQ No. 40

Which instrument is used to compare the e.m.f. of two cells accurately?

a. Voltmeter
b. Ammeter
c. Potentiometer
d. Galvanometer

Correct answer: c. Potentiometer

Explanation:
A potentiometer compares e.m.f. without drawing current from the cells.

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MCQ No. 41

The internal resistance of a cell is mainly due to:

a. Connecting wires
b. Electrolyte inside the cell
c. External resistor
d. Switch

Correct answer: b. Electrolyte inside the cell

Explanation:
The electrolyte offers resistance to the movement of ions.

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MCQ No. 42

Which law is represented by the equation ΣI = 0 at a junction?

a. Ohm's law
b. Kirchhoff's Current Law
c. Kirchhoff's Voltage Law
d. Joule's law

Correct answer: b. Kirchhoff's Current Law

Explanation:
The algebraic sum of currents at a junction is zero.

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MCQ No. 43

The terminal potential difference of a cell is always equal to its e.m.f. when:

a. It is supplying current
b. It is charging
c. No current flows
d. Internal resistance is infinite

Correct answer: c. No current flows

Explanation:
With zero current, there is no voltage drop across internal resistance.

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MCQ No. 44

A thermistor is primarily used as a:

a. Current source
b. Temperature-sensitive resistor
c. Capacitor
d. Fuse

Correct answer: b. Temperature-sensitive resistor

Explanation:
A thermistor changes its resistance significantly with temperature.

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MCQ No. 45

The SI unit of electrical power is:

a. Joule
b. Watt
c. Volt
d. Coulomb

Correct answer: b. Watt

Explanation:
Electrical power is measured in watts (W).

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MCQ No. 46

In a parallel combination of resistors, the potential difference across each resistor is:

a. Different
b. Zero
c. Equal
d. Infinite

Correct answer: c. Equal

Explanation:
All parallel branches are connected directly across the supply voltage.

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MCQ No. 47

Which of the following materials generally has the highest conductivity?

a. Glass
b. Copper
c. Rubber
d. Wood

Correct answer: b. Copper

Explanation:
Copper is an excellent electrical conductor due to its large number of free electrons.

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MCQ No. 48

The SI unit of resistivity is:

a. Ω
b. Ω m
c. Ω/m
d. S/m

Correct answer: b. Ω m

Explanation:
The SI unit of resistivity is ohm-meter (Ω m).

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MCQ No. 49

A conductor obeying Ohm's law has a graph between current and voltage that is:

a. Circular
b. Straight line through the origin
c. Hyperbola
d. Parabola

Correct answer: b. Straight line through the origin

Explanation:
For an ohmic conductor, current is directly proportional to voltage.

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MCQ No. 50

A potentiometer works on the principle that:

a. Current is constant in parallel circuits.
b. Potential drop is directly proportional to the length of a uniform wire carrying constant current.
c. Resistance decreases with temperature.
d. Power is proportional to voltage.

Correct answer: b. Potential drop is directly proportional to the length of a uniform wire carrying constant current.

Explanation:
A potentiometer uses the uniform potential gradient along a wire to measure or compare voltages with high accuracy.

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MCQ No. 51

The current through a conductor is directly proportional to the potential difference across it, provided:

a. Temperature remains constant
b. Resistance changes continuously
c. Length of conductor changes
d. Cross-sectional area changes

Correct answer: a. Temperature remains constant

Explanation:
Ohm's law is valid only when the physical conditions, especially temperature, remain constant.

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MCQ No. 52

The SI unit of electromotive force (e.m.f.) is the same as that of:

a. Current
b. Resistance
c. Potential difference
d. Power

Correct answer: c. Potential difference

Explanation:
Both electromotive force and potential difference are measured in volts (V).

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MCQ No. 53

Which one of the following is an example of a non-ohmic conductor?

a. Copper wire
b. Nichrome wire
c. Thermistor
d. Silver wire

Correct answer: c. Thermistor

Explanation:
A thermistor does not obey Ohm's law because its resistance changes significantly with temperature.

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MCQ No. 54

The reciprocal of conductivity is:

a. Conductance
b. Resistivity
c. Resistance
d. Current density

Correct answer: b. Resistivity

Explanation:
Resistivity (ρ) is the reciprocal of conductivity (σ).

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MCQ No. 55

The resistance of a conductor becomes half when its:

a. Length is doubled
b. Cross-sectional area is doubled
c. Resistivity is doubled
d. Temperature increases

Correct answer: b. Cross-sectional area is doubled

Explanation:
Since $R=\rho L/A$ , doubling the area reduces the resistance to half.

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MCQ No. 56

A resistor converts electrical energy mainly into:

a. Mechanical energy
b. Heat energy
c. Chemical energy
d. Light energy only

Correct answer: b. Heat energy

Explanation:
Electrical energy is converted into heat due to Joule heating.

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MCQ No. 57

The direction of conventional current is:

a. From negative to positive terminal outside the cell
b. Opposite to electron flow
c. Same as electron flow
d. Random inside a conductor

Correct answer: b. Opposite to electron flow

Explanation:
Conventional current flows from positive to negative, opposite to the direction of electron flow.

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MCQ No. 58

Which quantity remains unchanged when identical resistors are connected in series?

a. Equivalent resistance
b. Current through each resistor
c. Voltage across each resistor
d. Power dissipated in each resistor

Correct answer: b. Current through each resistor

Explanation:
The same current passes through every resistor in a series circuit.

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MCQ No. 59

A material having very low resistivity is generally called a:

a. Semiconductor
b. Conductor
c. Insulator
d. Dielectric

Correct answer: b. Conductor

Explanation:
Conductors possess very low resistivity, allowing current to flow easily.

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MCQ No. 60

The product of current and resistance gives:

a. Power
b. Charge
c. Potential difference
d. Conductance

Correct answer: c. Potential difference

Explanation:
According to Ohm's law, $V = IR$.

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MCQ No. 61

In a resistor, electrical energy is transformed into:

a. Mechanical energy
b. Heat energy
c. Nuclear energy
d. Magnetic energy only

Correct answer: b. Heat energy

Explanation:
The resistor dissipates electrical energy as heat.

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MCQ No. 62

The unit of electrical energy is:

a. Joule
b. Newton
c. Watt
d. Volt

Correct answer: a. Joule

Explanation:
The SI unit of energy, including electrical energy, is the joule.

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MCQ No. 63

The resistance of a metallic conductor increases because of:

a. Increase in free electrons
b. Increase in atomic vibrations
c. Decrease in temperature
d. Increase in conductivity

Correct answer: b. Increase in atomic vibrations

Explanation:
Higher temperature increases lattice vibrations, causing more collisions with electrons.

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MCQ No. 64

The current through an ideal voltmeter is:

a. Maximum
b. Zero
c. Equal to applied voltage
d. Infinite

Correct answer: b. Zero

Explanation:
An ideal voltmeter has infinite resistance and draws no current.

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MCQ No. 65

An ideal ammeter has:

a. Infinite resistance
b. Very high resistance
c. Zero resistance
d. High capacitance

Correct answer: c. Zero resistance

Explanation:
An ideal ammeter should not produce any voltage drop while measuring current.

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MCQ No. 66

Which law is used to analyze complex electrical networks?

a. Newton's law
b. Kirchhoff's laws
c. Boyle's law
d. Coulomb's law

Correct answer: b. Kirchhoff's laws

Explanation:
Kirchhoff's current and voltage laws are used for analyzing electrical circuits.

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MCQ No. 67

The temperature coefficient of resistance for pure metals is generally:

a. Negative
b. Zero
c. Positive
d. Infinite

Correct answer: c. Positive

Explanation:
The resistance of pure metals increases with temperature.

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MCQ No. 68

A potentiometer is preferred over a voltmeter because it:

a. Draws more current
b. Consumes more power
c. Measures voltage without drawing current from the source
d. Measures current directly

Correct answer: c. Measures voltage without drawing current from the source

Explanation:
The potentiometer works on the null method and therefore provides highly accurate measurements.

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MCQ No. 69

The Wheatstone bridge is mainly used to:

a. Measure electric power
b. Measure unknown resistance
c. Measure current
d. Produce alternating current

Correct answer: b. Measure unknown resistance

Explanation:
The Wheatstone bridge accurately determines an unknown resistance by balancing the bridge.

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MCQ No. 70

At the balance point of a Wheatstone bridge, the galvanometer shows:

a. Maximum current
b. Infinite current
c. Zero current
d. High voltage

Correct answer: c. Zero current

Explanation:
At balance, the potential difference across the galvanometer is zero.

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MCQ No. 71

The electrical power consumed by a resistor is proportional to:

a. Current only
b. Voltage only
c. Current squared and resistance
d. Resistance only

Correct answer: c. Current squared and resistance

Explanation:
Electrical power is given by $P = I^2R$.

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MCQ No. 72

A wire of low resistivity is generally used for:

a. Heating elements
b. Connecting wires
c. Electric heaters
d. Fuse wires

Correct answer: b. Connecting wires

Explanation:
Connecting wires should have low resistance to minimize power loss.

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MCQ No. 73

The SI unit of conductivity is:

a. Ω m
b. Ω⁻¹ m⁻¹ (S m⁻¹)
c. Volt
d. Ampere

Correct answer: b. Ω⁻¹ m⁻¹ (S m⁻¹)

Explanation:
The SI unit of conductivity is siemens per metre (S m⁻¹), also written as Ω⁻¹ m⁻¹.

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MCQ No. 74

The main function of a potential divider is to:

a. Increase current
b. Divide supplied voltage into required values
c. Increase resistance only
d. Store electrical energy

Correct answer: b. Divide supplied voltage into required values

Explanation:
A potential divider provides different output voltages from a single source.

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MCQ No. 75

The voltage drop across the internal resistance of a cell is equal to:

a. Ir
b. IR
c. V/R
d. ε/R

Correct answer: a. Ir

Explanation:
The voltage lost inside the cell due to its internal resistance is given by Ir, where I is the current and r is the internal resistance.

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MCQ No. 76

A conductor offers opposition to the flow of electric current due to its:

a. Capacitance
b. Resistance
c. Inductance
d. Conductance

Correct answer: b. Resistance

Explanation:
Resistance is the property of a conductor that opposes the flow of electric current.

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MCQ No. 77

The SI unit of conductance is:

a. Ohm (Ω)
b. Siemens (S)
c. Volt (V)
d. Ampere (A)

Correct answer: b. Siemens (S)

Explanation:
Conductance is the reciprocal of resistance, and its SI unit is siemens (S).

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MCQ No. 78

The drift velocity of free electrons depends upon:

a. Applied electric field
b. Colour of the conductor
c. Shape of the conductor only
d. Density of air around the conductor

Correct answer: a. Applied electric field

Explanation:
Drift velocity increases with the strength of the applied electric field.

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MCQ No. 79

The resistance of a conductor is independent of its:

a. Length
b. Material
c. Cross-sectional area
d. Colour

Correct answer: d. Colour

Explanation:
Resistance depends on length, area, material, and temperature—not on colour.

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MCQ No. 80

A battery converts:

a. Mechanical energy into electrical energy
b. Chemical energy into electrical energy
c. Heat energy into electrical energy
d. Light energy into electrical energy

Correct answer: b. Chemical energy into electrical energy

Explanation:
A battery supplies electrical energy by converting stored chemical energy.

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MCQ No. 81

Which of the following devices is commonly used as a variable resistor?

a. Capacitor
b. Rheostat
c. Fuse
d. Diode

Correct answer: b. Rheostat

Explanation:
A rheostat is a variable resistor used to control current in a circuit.

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MCQ No. 82

The resistance of an ideal conductor is:

a. Infinite
b. One ohm
c. Zero
d. Very high

Correct answer: c. Zero

Explanation:
An ideal conductor offers no opposition to the flow of current.

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MCQ No. 83

If the potential difference across a resistor is zero, the current through it will be:

a. Infinite
b. Zero
c. Maximum
d. Unchanged

Correct answer: b. Zero

Explanation:
According to Ohm's law, $I = V/R$ . When $V = 0$ , the current is also zero.

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MCQ No. 84

The purpose of a fuse in an electrical circuit is to:

a. Increase voltage
b. Store electrical energy
c. Protect the circuit from excessive current
d. Increase resistance permanently

Correct answer: c. Protect the circuit from excessive current

Explanation:
A fuse melts when excessive current flows, protecting electrical appliances.

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MCQ No. 85

A good conductor generally has:

a. High resistivity
b. Low conductivity
c. Low resistivity
d. Infinite resistance

Correct answer: c. Low resistivity

Explanation:
Good conductors have very low resistivity, allowing current to flow easily.

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MCQ No. 86

The SI unit of electric charge is:

a. Ampere
b. Coulomb
c. Volt
d. Joule

Correct answer: b. Coulomb

Explanation:
The coulomb (C) is the SI unit of electric charge.

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MCQ No. 87

The mathematical expression for electrical power is:

a. P = VI
b. P = V/I
c. P = IR
d. P = R/I

Correct answer: a. P = VI

Explanation:
Electrical power is the product of potential difference and current.

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MCQ No. 88

In a metallic conductor, charge is carried by:

a. Positive ions only
b. Negative ions only
c. Free electrons
d. Protons

Correct answer: c. Free electrons

Explanation:
The movement of free electrons is responsible for electric current in metals.

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MCQ No. 89

The Wheatstone bridge is balanced when:

a. Current through every resistor is equal
b. Potential difference across the galvanometer is zero
c. Resistance of every arm is identical
d. Supply voltage becomes zero

Correct answer: b. Potential difference across the galvanometer is zero

Explanation:
At balance, no current flows through the galvanometer.

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MCQ No. 90

A conductor with higher conductivity will have:

a. Higher resistivity
b. Lower resistivity
c. Higher resistance only
d. Infinite resistance

Correct answer: b. Lower resistivity

Explanation:
Conductivity and resistivity are reciprocals of each other.

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MCQ No. 91

A thermocouple is used to convert:

a. Heat energy into electrical energy
b. Electrical energy into heat energy
c. Mechanical energy into electrical energy
d. Light energy into electrical energy

Correct answer: a. Heat energy into electrical energy

Explanation:
A thermocouple produces an e.m.f. when its junctions are at different temperatures.

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MCQ No. 92

The balance point in a potentiometer is called the:

a. Null point
b. Midpoint
c. Current point
d. Resistance point

Correct answer: a. Null point

Explanation:
At the null point, no current flows through the galvanometer.

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MCQ No. 93

The temperature coefficient of resistance indicates:

a. Change in current with voltage
b. Change in resistance with temperature
c. Change in voltage with time
d. Change in power with current

Correct answer: b. Change in resistance with temperature

Explanation:
It measures how much the resistance changes per degree change in temperature.

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MCQ No. 94

Which law states that the algebraic sum of potential differences around any closed loop is zero?

a. Ohm's Law
b. Kirchhoff's Current Law
c. Kirchhoff's Voltage Law
d. Joule's Law

Correct answer: c. Kirchhoff's Voltage Law

Explanation:
Kirchhoff's Voltage Law follows the principle of conservation of energy.

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MCQ No. 95

A resistor having a negative temperature coefficient is generally:

a. Copper
b. Aluminium
c. Thermistor
d. Silver

Correct answer: c. Thermistor

Explanation:
The resistance of most thermistors decreases as temperature increases.

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MCQ No. 96

The current supplied by a source depends upon:

a. The total resistance of the circuit
b. The colour of the connecting wire
c. The shape of the battery
d. The size of the switch

Correct answer: a. The total resistance of the circuit

Explanation:
According to Ohm's law, current depends on the applied voltage and total circuit resistance.

---

MCQ No. 97

The equivalent resistance of resistors connected in parallel is always:

a. Greater than the largest resistance
b. Equal to the largest resistance
c. Less than the smallest resistance
d. Equal to the smallest resistance

Correct answer: c. Less than the smallest resistance

Explanation:
The equivalent resistance of parallel resistors is always smaller than the smallest individual resistance.

---

MCQ No. 98

Electrical conductivity mainly depends upon the number of:

a. Molecules
b. Free charge carriers
c. Neutrons
d. Atomic nuclei

Correct answer: b. Free charge carriers

Explanation:
Materials with a greater number of free charge carriers have higher conductivity.

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MCQ No. 99

The efficiency of electrical transmission is improved by using conductors having:

a. High resistivity
b. Low conductivity
c. Low resistance
d. High temperature coefficient

Correct answer: c. Low resistance

Explanation:
Low-resistance conductors minimize power loss during transmission.

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MCQ No. 100

Which one of the following provides the most accurate measurement of e.m.f.?

a. Ammeter
b. Voltmeter
c. Potentiometer
d. Galvanometer

Correct answer: c. Potentiometer

Explanation:
A potentiometer measures e.m.f. using the null method without drawing current from the source, making it more accurate than a voltmeter.

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