Current Electricity Top 100 MCQs With Answer and Explanation

What is the SI unit of electric current?
a) Volt
b) Ampere
c) Ohm
d) Watt
Answer: b) Ampere
Explanation: Electric current is measured in amperes (A), which represents the flow of charge per second.
Which device is used to measure electric current?
a) Voltmeter
b) Ammeter
c) Ohmmeter
d) Galvanometer
Answer: b) Ammeter
Explanation: An ammeter is connected in series in a circuit to measure current.
Ohm’s law states that the current through a conductor is directly proportional to the:
a) Voltage across the conductor
b) Resistance of the conductor
c) Power supplied
d) Temperature of the conductor
Answer: a) Voltage across the conductor
Explanation: Ohm’s law is .
The resistance of a conductor depends on:
a) Length of the conductor
b) Cross-sectional area
c) Temperature
d) All of the above
Answer: d) All of the above
Explanation: Resistance , and it changes with temperature.
If the length of a wire is doubled, keeping the same material and cross-sectional area, the resistance will:
a) Double
b) Halve
c) Become four times
d) Remain the same
Answer: a) Double
Explanation: Resistance is directly proportional to length.
The unit of resistivity is:
a) Ohm meter
b) Ohm per meter
c) Meter per ohm
d) Ohm
Answer: a) Ohm meter
Explanation: Resistivity has units of ohm meter (Ω·m).
A material which has very low resistivity is called:
a) Insulator
b) Conductor
c) Semiconductor
d) Superconductor
Answer: b) Conductor
Explanation: Conductors have low resistivity, allowing easy current flow.
Superconductors have:
a) Zero resistance below a critical temperature
b) Infinite resistance
c) Very high resistance
d) Constant resistance at all temperatures
Answer: a) Zero resistance below a critical temperature
Explanation: Superconductors exhibit zero resistance at low temperatures.
The drift velocity of electrons in a conductor:
a) Is very high
b) Is zero
c) Is very small compared to speed of electric signals
d) Equals the speed of light
Answer: c) Is very small compared to speed of electric signals
Explanation: Electron drift velocity is slow; electric signals propagate close to light speed.
Which of the following is NOT a factor affecting resistance?
a) Length
b) Area
c) Temperature
d) Current
Answer: d) Current
Explanation: Resistance depends on material properties, length, area, and temperature but not on current.
The formula for power in an electric circuit is:
a)
b)
c)
d)
Answer: a)
Explanation: Power is voltage times current.
In a series circuit, the total resistance is:
a) The sum of individual resistances
b) The product of individual resistances
c) Less than any individual resistance
d) The reciprocal of the sum of reciprocals
Answer: a) The sum of individual resistances
Explanation:
In a parallel circuit, the total resistance is:
a) Sum of resistances
b) Product over sum of resistances
c) Reciprocal of sum of reciprocals
d) Always greater than the smallest resistance
Answer: c) Reciprocal of sum of reciprocals
Explanation:
The potential difference across resistors connected in series:
a) Is the same
b) Adds up to total voltage
c) Is zero
d) None of the above
Answer: b) Adds up to total voltage
Explanation: Voltage divides among resistors in series.
The potential difference across resistors connected in parallel:
a) Is the same
b) Adds up to total voltage
c) Is zero
d) None of the above
Answer: a) Is the same
Explanation: Voltage across parallel resistors is equal.
The resistance of a wire depends on the temperature. For metals, as temperature increases, resistance:
a) Increases
b) Decreases
c) Remains constant
d) Varies randomly
Answer: a) Increases
Explanation: Metals resistivity increases with temperature.
An ohmic conductor is one which:
a) Follows Ohm’s law
b) Has zero resistance
c) Has resistance increasing with temperature
d) Is a semiconductor
Answer: a) Follows Ohm’s law
Explanation: Ohmic conductors have linear V-I characteristics.
If the current in a circuit is doubled, the power dissipated:
a) Doubles
b) Quadruples
c) Halves
d) Remains the same
Answer: b) Quadruples
Explanation: , so power varies as square of current.
Kirchhoff’s first law is based on:
a) Conservation of energy
b) Conservation of charge
c) Conservation of momentum
d) Ohm’s law
Answer: b) Conservation of charge
Explanation: Current entering a junction equals current leaving.
The total current flowing in a parallel circuit is:
a) Equal to the current in each branch
b) Sum of currents in all branches
c) Product of currents in all branches
d) Zero
Answer: b) Sum of currents in all branches
Explanation: Current divides in parallel branches and sums up.
What happens to the resistance of a wire if its cross-sectional area is doubled?
a) Resistance doubles
b) Resistance halves
c) Resistance quadruples
d) Resistance remains same
Answer: b) Resistance halves
Explanation: Resistance , so doubling area halves resistance.
Which of the following materials is a good conductor of electricity?
a) Copper
b) Glass
c) Rubber
d) Wood
Answer: a) Copper
Explanation: Copper has low resistivity and allows free flow of electrons.
What is the direction of conventional current?
a) From negative to positive terminal
b) From positive to negative terminal
c) Random direction
d) None of the above
Answer: b) From positive to negative terminal
Explanation: Conventional current flows from positive to negative externally.
In a circuit, if resistance remains constant and voltage is doubled, current:
a) Halves
b) Doubles
c) Remains the same
d) Quadruples
Answer: b) Doubles
Explanation: , so doubling doubles .
The power dissipated in a resistor is maximum when:
a) Voltage is maximum
b) Current is maximum
c) Resistance is zero
d) Resistance matches the load
Answer: d) Resistance matches the load
Explanation: Maximum power transfer theorem states max power when load resistance = source resistance.
In metals, the charge carriers are:
a) Protons
b) Electrons
c) Neutrons
d) Ions
Answer: b) Electrons
Explanation: Free electrons carry charge in metals.
Which of these quantities does NOT change in a parallel circuit?
a) Voltage
b) Current
c) Resistance
d) Power
Answer: a) Voltage
Explanation: Voltage remains the same across all parallel branches.
If the voltage across a wire is doubled, the power dissipated in it:
a) Doubles
b) Quadruples
c) Halves
d) Remains constant
Answer: b) Quadruples
Explanation: , power depends on square of voltage.
The SI unit of resistance is:
a) Volt
b) Ampere
c) Ohm
d) Watt
Answer: c) Ohm
Explanation: Resistance is measured in ohms (Ω).
Which instrument is used to measure voltage?
a) Ammeter
b) Voltmeter
c) Ohmmeter
d) Wattmeter
Answer: b) Voltmeter
Explanation: Voltmeter measures potential difference across two points.
If two resistors of 6 Ω and 3 Ω are connected in series, their equivalent resistance is:
a) 2 Ω
b) 9 Ω
c) 1 Ω
d) 18 Ω
Answer: b) 9 Ω
Explanation: Series resistance adds: Ω.
If the same two resistors are connected in parallel, the equivalent resistance is:
a) 2 Ω
b) 9 Ω
c) 1 Ω
d) 18 Ω
Answer: a) 2 Ω
Explanation: .
The resistance of a semiconductor:
a) Increases with temperature
b) Decreases with temperature
c) Is constant with temperature
d) Is zero at room temperature
Answer: b) Decreases with temperature
Explanation: Semiconductors conduct better at higher temperatures.
The resistor used to control current in a circuit is called:
a) Ammeter
b) Rheostat
c) Galvanometer
d) Capacitor
Answer: b) Rheostat
Explanation: Rheostat varies resistance to control current.
The energy dissipated in an electric circuit is measured in:
a) Joules
b) Watts
c) Amperes
d) Volts
Answer: a) Joules
Explanation: Energy = Power × Time, measured in joules (J).
The heating effect of electric current is the basis for:
a) Electric motor
b) Electric heater
c) Battery
d) Dynamo
Answer: b) Electric heater
Explanation: Current through resistance produces heat.
Electric current is defined as:
a) Flow of electrons
b) Flow of protons
c) Rate of flow of charge
d) Rate of flow of neutrons
Answer: c) Rate of flow of charge
Explanation: Current = charge per unit time (I = Q/t).
The drift velocity of electrons depends on:
a) Current
b) Number density of electrons
c) Cross-sectional area of conductor
d) All of the above
Answer: d) All of the above
Explanation: , drift velocity .
When resistors are connected in series, the voltage across each resistor is:
a) Same
b) Different
c) Zero
d) None
Answer: b) Different
Explanation: Voltage divides among resistors in series.
When resistors are connected in parallel, the current through each resistor is:
a) Same
b) Different
c) Zero
d) None
Answer: b) Different
Explanation: Current divides in parallel branches according to resistance.
Which law states the sum of voltage drops equals the total emf in a closed circuit?
a) Ohm’s Law
b) Kirchhoff’s Voltage Law
c) Kirchhoff’s Current Law
d) Faraday’s Law
Answer: b) Kirchhoff’s Voltage Law
Explanation: Sum of emf = sum of potential drops in a loop.
What is the current flowing through a 5 Ω resistor when a voltage of 20 V is applied?
a) 4 A
b) 5 A
c) 15 A
d) 25 A
Answer: a) 4 A
Explanation: A.
The emf of a battery is 12 V and the internal resistance is 1 Ω. If the current is 2 A, the terminal voltage is:
a) 14 V
b) 10 V
c) 12 V
d) 2 V
Answer: b) 10 V
Explanation: V.
A voltmeter is connected:
a) In series
b) In parallel
c) Either in series or parallel
d) None of these
Answer: b) In parallel
Explanation: To measure voltage, voltmeter is connected across points.
An ammeter has:
a) High resistance
b) Low resistance
c) Zero resistance
d) Infinite resistance
Answer: b) Low resistance
Explanation: To not affect current, ammeter resistance is very low.
The resistance of a wire is 10 Ω at 0°C. If the temperature coefficient of resistance is 0.004 per °C, resistance at 25°C is:
a) 12 Ω
b) 11 Ω
c) 10.5 Ω
d) 15 Ω
Answer: a) 12 Ω
Explanation: .

Correction: Ω

So Answer is b) 11 Ω.

What is the main reason for the resistance in metallic conductors?
a) Collisions of electrons with ions
b) Collisions of electrons with electrons
c) Presence of protons
d) Magnetic field
Answer: a) Collisions of electrons with ions
Explanation: Electron scattering causes resistance.
The resistivity of copper is approximately:
a)
b)
c)
d)
Answer: a)
Explanation: Copper is an excellent conductor with low resistivity.
The potential difference across a 4 Ω resistor carrying 3 A current is:
a) 12 V
b) 7 V
c) 1.33 V
d) 0.75 V
Answer: a) 12 V
Explanation: V.
In a circuit, if power is kept constant and voltage is increased, current:
a) Increases
b) Decreases
c) Remains constant
d) Zero
Answer: b) Decreases
Explanation: , for constant , if increases, decreases.
The SI unit of resistivity is:
a) Ω·m
b) Ω/m
c) m/Ω
d) Ω·cm
Answer: a) Ω·m
Explanation: Resistivity units are ohm meter.
Which component converts chemical energy into electrical energy?
a) Resistor
b) Battery
c) Capacitor
d) Inductor
Answer: b) Battery
Explanation: Batteries supply emf via chemical reactions.
If a wire of length and area has resistance , the resistance of a wire of length and area is:
a)
b)
c)
d)
Answer: b)
Explanation: . Doubling both and cancels out.
What happens to resistance when the temperature of a conductor increases?
a) Resistance increases
b) Resistance decreases
c) Resistance remains the same
d) Resistance becomes zero
Answer: a) Resistance increases
Explanation: Higher temperature causes more collisions, increasing resistance.
The charge on one mole of electrons is:
a)
b)
c)
d)
Answer: a)
Explanation: One mole has Avogadro’s number of electrons.
The work done in moving 1 coulomb charge through a potential difference of 1 volt is:
a) 1 joule
b) 1 watt
c) 1 ampere
d) 1 ohm
Answer: a) 1 joule
Explanation: Work = charge × voltage.
The current in a circuit is zero if:
a) Voltage is zero
b) Resistance is infinite
c) Both voltage zero and resistance infinite
d) None of the above
Answer: c) Both voltage zero and resistance infinite
Explanation: No voltage or infinite resistance means no current.
If the power dissipated in a resistor is 100 W and the current through it is 5 A, the resistance is:
a) 4 Ω
b) 5 Ω
c) 2 Ω
d) 1 Ω
Answer: a) 4 Ω
Explanation: .
In a metallic conductor, the free electrons originate from:
a) Outermost shell of metal atoms
b) Innermost shell
c) Protons
d) Neutrons
Answer: a) Outermost shell of metal atoms
Explanation: Valence electrons become free to conduct.
In a circuit, the electric power is measured in:
a) Volts
b) Amperes
c) Watts
d) Ohms
Answer: c) Watts
Explanation: Power is the rate of energy transfer measured in watts (W).
What is the resistance of a wire of length 2 m and cross-sectional area , if resistivity is ?
a) 0.034 Ω
b) 34 Ω
c) 0.17 Ω
d) 170 Ω
Answer: a) 0.034 Ω
Explanation: .
Which of the following has zero electrical resistance?
a) Copper
b) Superconductor
c) Silicon
d) Graphite
Answer: b) Superconductor
Explanation: Superconductors exhibit zero resistance below critical temperature.
If 2 A current flows through a wire for 5 seconds, the charge passed is:
a) 2.5 C
b) 7 C
c) 10 C
d) 0.4 C
Answer: c) 10 C
Explanation: Coulombs.
The electrical resistance of a wire depends on its:
a) Length and material only
b) Length, material, and cross-sectional area
c) Temperature only
d) Temperature and voltage
Answer: b) Length, material, and cross-sectional area
Explanation: Resistance depends on length, resistivity (material), and area.
The direction of electron flow in a circuit is:
a) From positive to negative terminal
b) From negative to positive terminal
c) Same as conventional current
d) Random
Answer: b) From negative to positive terminal
Explanation: Electrons flow opposite to conventional current.
What is the power dissipated in a 10 Ω resistor carrying 2 A current?
a) 20 W
b) 40 W
c) 10 W
d) 100 W
Answer: b) 40 W
Explanation: .
The internal resistance of a battery causes:
a) Increase in emf
b) Decrease in terminal voltage
c) No effect on voltage
d) Increase in current beyond emf
Answer: b) Decrease in terminal voltage
Explanation: Terminal voltage , internal resistance causes voltage drop.
The resistance of a wire of length 1 m and area is 1 Ω. What will be the resistance if the wire is stretched to double the length and diameter is halved?
a) 4 Ω
b) 8 Ω
c) 2 Ω
d) 16 Ω
Answer: b) 8 Ω
Explanation: Resistance . Length doubled → , diameter halved → area quartered (). New resistance = Ω.
If two resistors of resistances R and 3R are connected in parallel, the equivalent resistance is:
a) 4R
b)
c)
d) 2R
Answer: b)
Explanation: . So, .
The emf of a cell is 12 V and its internal resistance is 0.5 Ω. When a current of 3 A flows, the terminal voltage is:
a) 12.5 V
b) 10.5 V
c) 13.5 V
d) 15 V
Answer: b) 10.5 V
Explanation: .
Which of the following is a non-ohmic device?
a) Resistor
b) Filament bulb
c) Copper wire
d) Nichrome wire
Answer: b) Filament bulb
Explanation: Its resistance changes with temperature, so it doesn’t obey Ohm’s law.
The emf of a source is 24 V and the resistance of the circuit is 3 Ω. What is the current?
a) 6 A
b) 8 A
c) 12 A
d) 18 A
Answer: a) 8 A
Explanation: Current A.
The SI unit of resistivity is:
a) Ω/m
b) Ω·m
c) m/Ω
d) Ω·cm
Answer: b) Ω·m
Explanation: Resistivity units are ohm meter.
Which law is used to find current and voltage in complex circuits?
a) Newton’s Law
b) Kirchhoff’s Law
c) Ohm’s Law
d) Faraday’s Law
Answer: b) Kirchhoff’s Law
Explanation: Kirchhoff’s current and voltage laws apply in circuit analysis.
If current in a wire is doubled, how is the heat produced affected?
a) Doubled
b) Quadrupled
c) Halved
d) Unchanged
Answer: b) Quadrupled
Explanation: Heat produced , so doubling current quadruples heat.
The resistance of a wire of length 1 m and cross-sectional area 1 mm² is 1 Ω. What is the resistance of the wire if length becomes 0.5 m and diameter doubled?
a) 2 Ω
b) 0.5 Ω
c) 0.25 Ω
d) 4 Ω
Answer: c) 0.25 Ω
Explanation: Length halved → , diameter doubled → area , resistance of original. So Ω (closest is 0.25 Ω assuming approximations).
Which of the following is NOT true about an ideal ammeter?
a) Connected in series
b) Has zero resistance
c) Measures current
d) Connected in parallel
Answer: d) Connected in parallel
Explanation: Ammeter must be connected in series.
In an electric circuit, the device used to regulate current is:
a) Rheostat
b) Voltmeter
c) Ammeter
d) Battery
Answer: a) Rheostat
Explanation: Rheostat varies resistance to control current flow.
If a current of 3 A flows through a wire for 4 minutes, the total charge that passes is:
a) 720 C
b) 12 C
c) 75 C
d) 60 C
Answer: a) 720 C
Explanation: .
What is the function of a galvanometer?
a) Measure current
b) Measure voltage
c) Measure resistance
d) Store energy
Answer: a) Measure current
Explanation: Galvanometer detects and measures small currents.
The electric power dissipated by a device is 60 W and voltage across it is 120 V. What is the current?
a) 0.5 A
b) 2 A
c) 60 A
d) 180 W
Answer: a) 0.5 A
Explanation: .
The resistivity of a metal depends primarily on:
a) Length of the wire
b) Temperature
c) Voltage applied
d) Current flowing
Answer: b) Temperature
Explanation: Resistivity varies with temperature.
For a constant voltage, if resistance is increased, power dissipated:
a) Increases
b) Decreases
c) Remains same
d) None of the above
Answer: b) Decreases
Explanation: , power decreases as resistance increases.
What happens to current when resistors are connected in series?
a) Same in all resistors
b) Splits among resistors
c) Zero
d) Increases
Answer: a) Same in all resistors
Explanation: Current is the same throughout series circuit.
In which case is the total resistance minimum?
a) Resistors connected in series
b) Resistors connected in parallel
c) Single resistor
d) None
Answer: b) Resistors connected in parallel
Explanation: Parallel connection reduces total resistance.
The voltage across each resistor in a parallel circuit is:
a) Same
b) Different
c) Zero
d) Depends on resistance
Answer: a) Same
Explanation: Voltage across parallel branches is equal.
Which is the best conductor among the following?
a) Copper
b) Iron
c) Aluminium
d) Lead
Answer: a) Copper
Explanation: Copper has lowest resistivity among these.
If the current through a wire is zero, the drift velocity is:
a) Maximum
b) Zero
c) Infinity
d) Unknown
Answer: b) Zero
Explanation: No current means no net movement of charge carriers.
A current of 1 A means:
a) One coulomb per second
b) One volt per second
c) One ohm per second
d) One watt per second
Answer: a) One coulomb per second
Explanation: Ampere is rate of charge flow.
In which direction do electrons move inside a conductor?
a) Same as current
b) Opposite to current
c) Random
d) None
Answer: b) Opposite to current
Explanation: Electron flow is opposite to conventional current.
If resistance and voltage are doubled, the current will be:
a) Same
b) Doubled
c) Halved
d) Quadrupled
Answer: a) Same
Explanation: , both numerator and denominator doubled cancel out.
The unit of electrical power is:
a) Volt
b) Watt
c) Ampere
d) Ohm
Answer: b) Watt
Explanation: Power is measured in watts.
The resistance of a wire at temperature is given by:
a)
b)
c)
d)
Answer: a)
Explanation: Resistance increases linearly with temperature for metals.
The resistance of a wire is 5 Ω at 20°C. Its resistance at 40°C if per °C will be:
a) 5.4 Ω
b) 6 Ω
c) 4.5 Ω
d) 7 Ω
Answer: a) 5.4 Ω
Explanation: .
The current density is related to current and cross-sectional area by:
a)
b)
c)
d)
Answer: a)
Explanation: Current density is current per unit area.
The resistance of a wire depends on:
a) Only length
b) Only cross-sectional area
c) Length and cross-sectional area
d) Neither length nor area
Answer: c) Length and cross-sectional area
Explanation: Resistance .
Ohm’s law states that:
a)
b)
c)
d)
Answer: a)
Explanation: Voltage across a resistor is proportional to current.
In a series circuit with resistors 2 Ω, 3 Ω, and 5 Ω, the total resistance is:
a) 10 Ω
b) 15 Ω
c) 1 Ω
d) 0.3 Ω
Answer: a) 10 Ω
Explanation: Total resistance in series is sum