Electricity – important questions for Boards 2027
CBSE Class 10 Science
One ampere of current is the flow of: (A) one coulomb of charge per second (B) one joule of energy per second (C) one electron per second (D) one volt of potential difference per second
Answer
(A) one coulomb of charge per second — One ampere is constituted by the flow of one coulomb of charge per second.
Define electric current and write the equation relating current to the charge flowing through a conductor in a given time.
Answer
Electric current is expressed by the amount of charge flowing through a particular area in unit time. If a net charge Q flows across any cross-section of a conductor in time t, then the current I through the cross-section is I = Q/t.
What is an electric circuit? Explain what happens to the current when the circuit is broken, and state the direction of conventional current in a metallic circuit relative to electron flow.
Answer
1. A continuous and closed path through which electric current flows is called an electric circuit. 2. If the circuit is broken anywhere, current stops flowing, so the bulb does not glow. 3. In a metallic circuit, conventional current flows opposite to electron flow; its direction is from the cell’s positive terminal to its negative terminal through the circuit.
Define the resistance of a conductor and write the equation used to determine it. Define the ohm, then explain what happens to the current at a fixed voltage if the resistance is doubled.
Answer
Resistance is the property of a conductor to resist the flow of charges through it. For a given metallic wire at a fixed temperature, resistance is determined by R = V/I, where V is the potential difference across the ends of the conductor and I is the current flowing through it. The SI unit of resistance is the ohm, represented by Ω. A conductor has a resistance of 1 Ω when a potential difference of 1 V across its ends produces a current of 1 A; hence, 1 Ω = 1 V/1 A. According to Ohm’s law, I = V/R. At a fixed voltage, current is inversely proportional to resistance. Therefore, if the resistance is doubled, the current becomes half.
Name the metal used almost exclusively for electric-bulb filaments.
Answer
Tungsten is used almost exclusively for filaments of electric bulbs, whereas copper and aluminium are generally used for electrical transmission lines.
What does a switch do in a circuit? State the direction in which current flows through the components connected to a cell.
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Write the relationship between the equivalent resistance Rp and the individual resistances R₁, R₂ and R₃ when three resistors are connected in parallel. Briefly explain how this relationship follows from the potential difference and current in the branches.
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Explain the meaning of one watt-hour and one kilowatt-hour. State the relationship between the kilowatt-hour and joule, and between kilowatt and watt.
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Three resistors are connected in parallel. If the total current is I and the branch currents are I₁, I₂ and I₃, which relationship is correct? (A) I = I₁ = I₂ = I₃ (B) I = I₁ + I₂ + I₃ (C) I₁ = I₂ + I₃ (D) I = I₁ × I₂ × I₃
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Define the potential difference between two points in terms of work and charge. What does a potential difference of 1 V mean?
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33 more probable questions in this chapter, every one with a full answer.
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