Chapter 11 · Electricity

NCERT Class 10 Science Chapter 11 Intext Questions (Page 192)

All 2 questions of NCERT Class 10 Science Chapter 11 Intext Questions (Page 192) — Electricity — in the book's order, each with its answer and a step-by-step solution.

1. Q1
   What determines the ​rate ​at ​which energy ​is ​delivered by a ​current?
   Show answer

   Electric power, $P=VI$, set by the potential difference across the device and the current through it.

   The rate at which energy is delivered by a current is the electric power, $P$. It is determined by two things: the potential difference $V$ across the device, which is the energy given up by each coulomb, and the current $I$ through it, which is the number of coulombs passing each second. Hence $P=VI$, measured in watts ($1$ W $=1$ V $\times$ $1$ A $=1$ J/s). Using Ohm's law the same rate can be written $P=I^{2}R=V^2/R$, so for a device of fixed resistance it is settled by the supply voltage, or equally by the current it draws.

   Step-by-step solution →
2. 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.
   Show answer

   The motor's power is $P=1100$ W (1.1 kW), and it consumes $7.92\times 10^6$ J (2.2 kW h) in 2 h.

   The power of the motor is $P=VI=220\text{V}\times 5\text{A}=1100$ W $=1.1$ kW. Taking $2$ h $=7200$ s, the energy consumed is $E=Pt=1100\text{W}\times 7200\text{s}=7.92\times 10^6$ J, which in commercial units is $1.1\text{kW}\times 2\text{h}=2.2$ kW h.

   Step-by-step solution →