Current Electricity MCQs
The direction of conventional current is the same as the direction of flow of:
Electrons
Positive charges
Atoms
Neutrons
Ohm's law states that the current through a conductor is directly proportional to the:
Resistance
Potential difference
Length
Temperature
The SI unit of electric resistance is:
Volt (V)
Ampere (A)
Ohm (Ω)
Siemens (S)
A carbon resistor is colored with Brown, Black, Orange, and Gold bands. What is its resistance and tolerance?
100 Ω ± 10%
1 kΩ ± 5%
10 kΩ ± 5%
1 MΩ ± 10%
Resistivity is the resistance of a conductor of unit length and unit:
Volume
Cross-sectional area
Diameter
Mass
The reciprocal of resistivity is called:
Conductance
Resistance
Conductivity
Permittivity
For metallic conductors, the resistance increases with an increase in:
Pressure
Cross-sectional area
Temperature
Length
A thermistor is a temperature-dependent:
Capacitor
Resistor
Inductor
Diode
Electric power is given by the formula:
P = V/I
P = I²R
P = V/R
P = IR
An electric iron of resistance 50 Ω is connected to a 200 V source. What is the amount of heat energy produced in 30 seconds?
24000 J
800 J
1200 J
60000 J
The commercial unit of electrical energy is:
Joule
Watt
Kilowatt-hour (kWh)
Volt-Ampere
One kilowatt-hour is equal to:
3.6 × 10³ J
3.6 × 10⁶ J
36 × 10⁵ J
6.3 × 10⁵ J
Electromotive force (EMF) is most accurately described as:
A force that pushes electrons
The potential difference across a resistor
Energy supplied per unit charge by the source
The power dissipated in a circuit
The terminal potential difference of a battery is always less than its EMF when:
The battery is being charged
The circuit is open
The battery is discharging (supplying current)
The internal resistance is zero
Kirchhoff's first rule is a statement of the conservation of:
Kirchhoff's second rule is a statement of the conservation of:
Energy
Charge
Voltage
Current
A Wheatstone bridge is said to be balanced when:
A large current flows through the galvanometer
All four resistances are equal
The battery EMF is high
No current flows through the galvanometer
The condition for a balanced Wheatstone bridge is:
R₁/R₂ = R₄/R₃
R₁ + R₂ = R₃ + R₄
R₁/R₂ = R₃/R₄
R₁R₂ = R₃R₄
A potentiometer is an ideal device for measuring potential difference because:
It has a very high resistance
It is highly sensitive
It draws no current from the source being measured at the balance point
It is easy to use
In a potentiometer experiment, a cell of EMF 1.25 V gives a balance point at 35 cm length of the wire. If this cell is replaced by another cell and the balance point shifts to 63 cm, what is the EMF of the second cell?
To increase the sensitivity of a potentiometer, one should:
Increase the current through the potentiometer wire
Decrease the length of the potentiometer wire
Increase the length of the potentiometer wire
Decrease the resistance of the potentiometer wire
The drift velocity of free electrons in a conductor is of the order of:
3 × 10⁸ m/s
10⁻³ m/s
10³ m/s
0 m/s
If three resistors of 2 Ω, 3 Ω, and 6 Ω are connected in parallel, their equivalent resistance is:
The colour code for a resistor of 270 Ω with 5% tolerance is:
Red, Violet, Brown, Gold
Red, Violet, Black, Silver
Orange, Violet, Brown, Gold
Red, Violet, Orange, Gold
A wire of resistance R is stretched to double its original length. Its new resistance will be:
Which of the following is a non-ohmic device?
Copper wire
Carbon resistor
Semiconductor diode
Manganin wire
The temperature coefficient of resistance is negative for:
Metals
Semiconductors
Alloys like Nichrome
Insulators
A current of 2A flows through a 5 Ω resistor for 10 seconds. How much energy is dissipated as heat?
For maximum power output from a source, the external resistance must be:
Equal to the internal resistance of the source
Greater than the internal resistance
Less than the internal resistance
Zero
If two bulbs rated 60W and 100W are connected in series to a mains supply, which one will glow brighter?
The 100W bulb
The 60W bulb
Both will glow with the same brightness
Neither will glow
What is the primary function of a rheostat in a circuit?
To measure current
To provide a constant resistance
To vary the resistance and control the current
To measure potential difference
A galvanometer with a coil resistance of 95 Ω gives a full-scale deflection for a current of 5 mA. What is the value of the shunt resistance required to convert it into an ammeter of range 5 A?
The algebraic sum of potential changes around any closed loop in a circuit is:
Equal to the total EMF
Infinite
Zero
Dependent on the direction of the loop
A meter bridge is an application of which principle?
Ohm's Law
Wheatstone Bridge
Kirchhoff's Laws
Potentiometer principle
Charge carriers in electrolytes are:
Free electrons
Protons
Ions
Holes
An ideal ammeter has a resistance that is:
Infinitely large
Very small, ideally zero
Equal to the circuit resistance
Variable
Two bulbs are rated 25 W - 220 V and 100 W - 220 V. They are connected in series to a 440 V supply. Which bulb will fuse?
The 100 W bulb
The 25 W bulb
Both will fuse
Neither will fuse
An ideal voltmeter has a resistance that is:
Infinitely large
Very small, ideally zero
Equal to the circuit resistance
Negative
A charge of 90 Coulombs flows through a wire in 1 minute and 30 seconds. What is the electric current in the wire?
The specific resistance of a material depends on its:
Length
Cross-sectional area
Nature and temperature
Mass
If the potential difference across a conductor is doubled, the drift velocity of electrons will:
Be halved
Remain unchanged
Be doubled
Be quadrupled
High resistance and high melting point
Low resistance and high melting point
High resistance and low melting point
Low resistance and low melting point
What happens to the resistance of a semiconductor as its temperature increases?
Increases
Decreases
Remains constant
First increases, then decreases
A battery of EMF 10 V and internal resistance 1 Ω is connected to a 4 Ω resistor. The current in the circuit is:
In the previous question, what is the terminal potential difference across the battery?
Which material is commonly used for the wire of a potentiometer?
Copper
Manganin
Tungsten
Aluminum
If the length of a conductor is halved and its cross-sectional area is doubled, the new resistance will be:
Unchanged
Doubled
One-fourth
Four times
The slope of a Voltage-Current (V-I) graph for an ohmic conductor represents:
Resistivity
Resistance
Conductance
Power
A flow of 10⁷ electrons per second constitutes a current of:
1.6 × 10⁻¹² A
1.6 × 10⁻²⁶ A
10⁷ A
1.6 × 10⁻¹⁹ A
What is the equivalent resistance between points A and B if three 3 Ω resistors are arranged in a triangle?
The heating effect of current is described by:
Ohm's Law
Joule's Law
Faraday's Law
Coulomb's Law
A carbon resistor has bands of yellow, violet, and red. Its resistance is:
To convert a galvanometer into an ammeter, one needs to connect a:
High resistance in series
Low resistance in parallel
High resistance in parallel
Low resistance in series
To convert a galvanometer into a voltmeter, one needs to connect a:
High resistance in series
Low resistance in parallel
High resistance in parallel
Low resistance in series
A potential divider circuit is used to:
Get a variable voltage from a fixed voltage source
Measure an unknown EMF
Increase the voltage of a source
Measure the current in a circuit
What is the equivalent resistance between points A and B in a circuit where a 10 Ω and 30 Ω resistor are in series, and this combination is in parallel with a 20 Ω resistor?
The unit of conductivity is:
Ohm-meter (Ω-m)
Siemens per meter (S/m)
Ohm (Ω)
Siemens (S)
The random motion of free electrons in a conductor results in a net current of:
Infinity
Zero
A small constant value
A value dependent on temperature
A charge of 600 Coulombs passes through a point in a circuit in 5 minutes. The current is:
Superconductors are materials whose resistance drops to virtually zero below a certain:
Critical Pressure
Critical Temperature
Critical Voltage
Critical Current
Two resistors are connected in parallel. The equivalent resistance is always:
Greater than either of the individual resistances
Equal to the sum of the individual resistances
Less than the smallest of the individual resistances
Equal to the product of the individual resistances
A 100-watt bulb operates on a 200 V supply. The current flowing through the bulb is:
Internal resistance of a cell is the resistance offered by the:
Connecting wires
External resistor (load)
Electrolyte and electrodes of the cell
Voltmeter connected across it
A Potentiometer can be used to:
Measure large currents accurately
Compare the EMFs of two cells
Measure the charge on an electron
Generate a high voltage
The resistivity of an insulator is of the order of:
10⁻⁸ Ω-m
10⁻³ Ω-m
10¹² Ω-m
1 Ω-m
If the current in a circuit is doubled, the power dissipated, assuming resistance is constant, will:
Be halved
Be doubled
Become four times
Remain unchanged
The potential gradient of a potentiometer wire is defined as:
The total potential difference across the wire
Potential difference per unit length of the wire
The current flowing through the wire
The resistance of the wire per unit length
A Wheatstone bridge is most sensitive when:
All four resistances are very high
All four resistances are very low
All four resistances are of the same order of magnitude
The battery has a very high EMF
Kirchhoff's Junction Rule is applicable to:
Only DC circuits
Only AC circuits
Both AC and DC circuits
Only circuits with resistors
In the colour code for resistors, the silver band represents a tolerance of:
If two identical batteries of EMF E and internal resistance r are connected in parallel, the equivalent EMF and internal resistance are:
2E, 2r
E, r/2
2E, r/2
E/2, 2r
The unit of electromotive force (EMF) is the same as the unit of:
Force
Power
Potential Difference
Current
When a battery is being charged, its terminal potential difference (V) is related to its EMF (E) and internal resistance (r) by:
V = E - Ir
V = E + Ir
V = E
V = Ir
An NTC thermistor is a device where the resistance:
Increases with increasing temperature
Decreases with increasing temperature
Remains constant with temperature
Is independent of current
The energy dissipated by a resistor can be calculated using:
E = VIt
E = V/I
E = IR
E = V/t
If a voltmeter is connected in series in a circuit, the current will be:
Very high
Very low or nearly zero
Unchanged
The same as the voltage reading
A 2 kW electric heater is operated for 5 hours. If the cost per unit (kWh) is Rs. 9, what is the total cost of the energy consumed?
Rs. 18
Rs. 45
Rs. 90
Rs. 9000
In a household circuit, appliances are connected in parallel so that:
The total current is minimized
Each appliance gets the same voltage
The total power consumed is low
If one appliance fails, all others stop working
The relationship between current density (J), conductivity (σ), and electric field (E) is:
J = E / σ
J = σE
J = σ/E
J = E + σ
The SI unit of charge is the Coulomb. One Coulomb is equivalent to:
Ampere-second
Ampere per second
Volt per meter
Joule per Volt
Which device is based on the heating effect of current?
Electric Motor
Galvanometer
Electric Fuse
Transformer
A material with a resistivity between that of conductors and insulators is called a:
Superconductor
Semiconductor
Dielectric
Electrolyte
The slope of a current-voltage (I-V) graph represents:
Resistance
Conductance
Resistivity
Power
Ohm's law is NOT obeyed by:
Conductors at constant temperature
Electrolytes
Vacuum tubes and transistors
Carbon resistors
A battery of EMF 6 V and internal resistance 0.5 Ω is connected to a resistor. If the current in the circuit is 1.0 A, what is the resistance of the external resistor?
For a potentiometer to function properly, the EMF of the driver cell in the primary circuit must be:
Less than the EMF of the cell to be measured
Greater than the EMF of the cell to be measured
Exactly equal to the EMF of the cell to be measured
Zero
A shunt is a low-resistance wire connected in parallel with a galvanometer to convert it into:
A voltmeter
An ammeter
A potentiometer
A rheostat
What happens to the drift velocity of electrons if the cross-sectional area of a current-carrying wire is decreased, while the current remains constant?
It decreases
It increases
It remains the same
It becomes zero
The power dissipated in a circuit is 12W when the voltage is 6V. What is the resistance of the circuit?
In a meter bridge experiment, the null point is found at 40 cm from one end. If a known resistance of 6 Ω is in the left gap, the unknown resistance is:
If the temperature of a metallic conductor is decreased, the relaxation time of free electrons will:
Decrease
Increase
Remain the same
Become infinite
A battery with an EMF of 1.5 V is connected to a 0.5 Ω resistor, and a current of 2 A flows. The internal resistance of the battery is:
The resistance of a platinum wire is 5 Ω at 20°C. When it is placed in a furnace, its resistance becomes 20 Ω. If the temperature coefficient of resistance (α) is 0.004 /°C, find the temperature of the furnace.
Which of these is NOT a source of EMF?
A solar cell
A thermocouple
A resistor
An electric generator
The Ampere-hour (Ah) is a unit of:
Power
Electric Charge
Energy
Current
Other Physics Topics MCQs
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