In-text Questions — Electric Power — Electricity

1. 11 markNCERT Cl-10 Science, In-text Qs after §11.8, Q1

   What determines the rate at which energy is delivered by a current?

   Hint. This rate has its own name and its own formula in this chapter.

   Step 1 — Recall what 'rate of energy delivery' means. The rate at which energy is delivered or consumed is called power.

   Step 2 — State the formula. Since P = VI, it is the product of potential difference and current that determines this rate.

   ✦ Answer: The electric power, P = VI, determines the rate at which energy is delivered by a current.

   Where students slip. Naming only current or only voltage as the determining factor — power depends on the product of both, not either one alone.

2. 22 marksNCERT Cl-10 Science, In-text Qs after §11.8, Q2

   An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.

   Hint. Find power first, then multiply by the given time to get energy.

   Step 1 — Find the power. P = VI = 220 × 5 = 1100 W = 1.1 kW.

   Step 2 — Find the energy consumed in 2 hours. Since energy equals power times time, Energy = P × t = 1.1 kW × 2 h = 2.2 kWh.

   ✦ Answer: Power = 1100 W (1.1 kW); energy consumed in 2 hours = 2.2 kWh.

   Where students slip. Leaving the energy answer in watt-seconds instead of converting to the more natural kWh — since time is given in hours and power in kW, kWh is the appropriate practical unit here.

Solutions written by the tuition.in editorial team and checked against the NCERT Class 10 Science textbook, Reprint 2026-27 (jesc111.pdf) — seven in-text question sets (23 questions total, not 16 as some older manifests claim) plus one end-of-chapter Exercise (18 questions, correctly counted). Unchanged by rationalisation. Table 11.2's resistivity values (used for several answers) were read directly from the book, including nichrome's 100 × 10⁻⁶ Ω·m.. Questions are referenced from the NCERT textbook for identification.