Chapter 11 · Electricity

NCERT Class 10 Science Chapter 11 Intext Questions (Page 172)

All 3 questions of NCERT Class 10 Science Chapter 11 Intext Questions (Page 172) — Electricity — in the book's order, each with its answer and a step-by-step solution.

1. Q1
   What does ​an ​electric ​circuit mean?
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   An electric circuit is a continuous, closed path along which an electric current flows.

   An electric circuit means a continuous and closed path along which an electric current flows. It is made up of a source of potential difference (a cell or a battery), connecting wires, one or more electrical components such as a bulb or a resistor, and usually a switch or plug key; an ammeter may also be joined in series. When the key is closed the path is complete and a current flows round the loop, conventionally from the positive terminal of the cell through the components to its negative terminal. If the path is broken at any point — for example by opening the key — the current stops flowing everywhere in the circuit.

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2. Q2
   Define the unit of current.
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   One ampere is the current when one coulomb of charge flows through a cross-section in one second.

   The SI unit of electric current is the ampere (A), named after Andre-Marie Ampere. One ampere is the current constituted by the flow of one coulomb of charge through any cross-section of a conductor in one second: $1\text{A}=1\text{C}/1\text{s}=1{\text{C s}}^{-1}$. Smaller currents are measured in milliampere ($1\text{mA}=10^{-3}$ A) and microampere ($1\mu \text{A}=10^{-6}$ A).

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3. Q3
   Calculate ​the ​number of electrons ​constituting ​one ​coulomb ​of charge.
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   $n=6.25\times 10^{18}$: one coulomb of charge is carried by about $6.25\times 10^{18}$ electrons.

   $n=Q/e=1\text{C}÷(1.6\times 10^{-19}\text{C})=6.25\times 10^{18}$ electrons (to the two significant figures of $e$, $6.3\times 10^{18}$; the chapter quotes it as nearly $6\times 10^{18}$ electrons). The number is a pure count and carries no unit.

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