Class 10 Science · CBSE / NCERT

Electricity MCQ Quiz
Electric Current, Potential Difference & Ohm's Law

15 carefully crafted multiple-choice questions with detailed explanations. Check each answer instantly or submit all at once for your score.

15 Questions
5 Topics
Instant Explanations
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Topic 1: Electric Circuit & Electric Current
Question 1
In a steady-state closed electric circuit, what physically happens to the speed and net count of conduction electrons as they pass through a high-resistance nichrome wire compared to when they are flowing through the low-resistance copper connecting wires?
📘 Explanation In a single continuous series circuit loop, electric current must be identical everywhere to prevent accumulation of charge at any point. Because a high-resistance wire slows down the drift velocity of electrons, the local carrier density adjusts — but the net number of electrons crossing any boundary per second remains constant to maintain a steady current.
Question 2
An electric circuit contains a cell, a switch, and a small bulb. When the switch is flipped from "OFF" to "ON", the bulb glows almost instantly. What is the fundamental physical reason for this immediate response?
📘 Explanation Individual electrons drift at a very slow pace (often less than a millimetre per second). However, closing the switch instantly establishes an electric field through the conductor at nearly the speed of light. This field exerts a simultaneous force on all free electrons already present inside the bulb filament, making them move immediately.
Question 3
Consider a conducting wire through which a steady current is flowing. If you compare a thick section of the wire to a thinner section within the same continuous series loop, which statement is true regarding the electric current?
📘 Explanation Due to the principle of conservation of charge, the total charge entering a wire segment must equal the total charge leaving it per unit of time. Therefore, the total current (I) is independent of the cross-sectional area in a series path.
Topic 2: Unit of Current & Fundamental Quantities
Question 4
The SI unit of electric current is the Ampere (A). If a device draws a constant current of exactly 1 mA (1 milliampere), what is the approximate number of elementary electron charges crossing a given cross-section of the wire every single minute?
📘 Explanation Using I = Q/t → Q = I × t = 10⁻³ A × 60 s = 0.06 C. Using Q = n·e where e = 1.6 × 10⁻¹⁹ C, the number of electrons is n = 0.06 ÷ (1.6 × 10⁻¹⁹) = 3.75 × 1017.
Question 5
Electric current has a specific numeric magnitude and a well-defined directional flow, yet it is treated as a scalar quantity rather than a vector quantity. Why?
📘 Explanation Vector quantities must satisfy vector addition laws (like the parallelogram law). When two wires carrying current meet at an angle, the total resulting current is simply the scalar sum (I₁ + I₂), completely independent of the spatial geometric angle between the wires. Hence, current is a scalar.
Question 6
A lightning strike transfers a total charge of 20 Coulombs from a storm cloud to a lightning rod in a flash lasting 0.05 seconds. What is the average current generated during this rapid discharge?
📘 Explanation I = Q ÷ t = 20 C ÷ 0.05 s = 400 Amperes. Lightning involves enormous currents because it transfers large charge in a very short time.
Topic 3: Potential Difference & The Volt
Question 7
Which of the following analogies best explains the conceptual definition of "Potential Difference" between two distinct points in an active electrical circuit?
📘 Explanation Electric potential difference functions similarly to fluid pressure. Just as a difference in fluid pressure causes water to flow through a pipe, a difference in electric potential creates the "pressure" required to drive charges through a circuit. Mathematically: V = W / Q.
Question 8
By definition, a potential difference of exactly 1 Volt exists between two points in a current-carrying conductor when:
📘 Explanation By definition: Potential Difference V = W / Q. Therefore, 1 Volt = 1 Joule / 1 Coulomb. Option B defines 1 Ampere (current), not 1 Volt.
Question 9
A battery does 60 Joules of electrical work to move a specific bundle of electric charge through a heating element. If the potential difference maintained across the element is 12 Volts, how much charge was pushed through the circuit?
📘 Explanation Rearranging V = W / Q gives Q = W / V = 60 J ÷ 12 V = 5.0 Coulombs.
Topic 4: Ohm's Law & V-I Relationships
Question 10
According to Ohm's Law, the current flowing through a metallic conductor is directly proportional to the potential difference applied across its ends, provided that:
📘 Explanation Ohm's Law (V ∝ I) is an empirical rule that holds true only if the internal structure and physical state of the conductor do not change. An increase in temperature increases the resistance of metallic conductors, breaking the linear proportionality between V and I.
Question 11
A student plots a V vs I graph for two metallic wires, Wire X and Wire Y. The straight line for Wire X is steeper (larger angle with the horizontal I-axis) than the line for Wire Y. What does this indicate?
📘 Explanation On a V–I graph, the slope (ΔV / ΔI) represents resistance R. A steeper line → larger slope → higher resistance. Wire X is steeper, so Wire X has more resistance than Wire Y.
Question 12
A fixed cylindrical resistor obeys Ohm's Law perfectly. If the potential difference applied across this resistor is reduced to exactly one-third of its original value, what happens to its electrical resistance?
📘 Explanation Resistance R depends only on the material, length, and cross-sectional area of the resistor. Changing the external voltage alters the current proportionally, but does not modify the intrinsic physical resistance. R = ρL/A — no voltage term here!
Topic 5: Comprehensive Conceptual Integration
Question 13
An ammeter and a voltmeter are being connected to a circuit containing a resistor. To get accurate readings without altering the circuit's behaviour, how should they be connected and what should their ideal internal resistances be?
📘 Explanation An ammeter is connected in series (all current flows through it) and must have very low resistance so it doesn't reduce the circuit's current. A voltmeter is connected in parallel and must have very high resistance so it doesn't bypass current away from the main component being measured.
Question 14
If a steady current is maintained through a non-uniform metallic conductor whose cross-sectional area increases gradually from left to right, how do the current (I) and the drift speed (vd) of the electrons vary along this conductor?
📘 Explanation Current (I) must remain uniform throughout a single path to satisfy charge conservation. The relationship is I = nAevd. As the cross-sectional area A increases from left to right, the drift velocity vd must decrease proportionally to keep I constant.
Question 15
A metallic wire obeys Ohm's Law. If the voltage is doubled while the wire is simultaneously stretched uniformly to double its original length at a constant temperature, the final current in the wire will be:
📘 Explanation When stretched to double length: new length L' = 2L, new area A' = A/2 (volume conserved). New resistance R' = ρ(2L)/(A/2) = 4R. New voltage V' = 2V. New current I' = V'/R' = 2V/4R = ½ I. The current is halved.

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⚠️ Disclaimer: This quiz is created for educational purposes to help Class 10 students prepare for CBSE board exams. While every effort has been made to ensure accuracy, there may be typographical or factual errors. In case of any doubt, please verify the information from your NCERT textbook or consult your subject teacher. EduBrightPages does not guarantee 100% accuracy and shall not be held responsible for any discrepancies. Content is based on the NCERT Class 10 Science curriculum (Chapter 12 – Electricity).