✓ Board-verified
Science · 2023 · 5 marks
CBSE 2023 · Region 5 · Set 3 · Q35
(a) Define electric power and state its SI unit. The commercial unit of electrical energy is known as 'unit'. Write the relation between this 'unit'…
(a)
Define electric power and state its SI unit. The commercial unit of electrical energy is known as 'unit'. Write the relation between this 'unit' and joule.
(b)
In a house, $\displaystyle 2$ bulbs of $\displaystyle 50$ W each are used for $\displaystyle 6$ hours daily and an electric geyser of $\displaystyle 1$ kW is used for $\displaystyle 1$ hour daily. Calculate the total energy consumed in a month of $\displaystyle 30$ days and its cost at the rate of ₹ $\displaystyle 8.00$ per kWh.
Marking-scheme solution
(a) • The rate at which electrical energy is dissipated / consumed in a circuit.
Watt or W
$\displaystyle 1$ unit \(\displaystyle (1 \mathrm{kWh})=3 \cdot 6 \times 10^{6}\) joule \(\displaystyle (\mathrm{J})\)
(b) \(\displaystyle \mathrm{E}=\mathrm{P} \times \mathrm{T}\)
Electrical energy, \(\displaystyle \mathrm{E}_{1}\), consumed by $\displaystyle 2$ bulbs of $\displaystyle 50$ W each is
\[E_{1}=50 \times 2 \times 6=600 \mathrm{~Wh}
\]
Electrical energy, \(\displaystyle \mathrm{E}_{2}\), consumed by electric geyser of $\displaystyle 1$ kW is
\[E_{2}=1000 \times 1=1000 \mathrm{~Wh}
\]
Total energy consumed in the month of $\displaystyle 30$ days
\[\begin{aligned}
{\left[\mathrm{E}_{1}+\mathrm{E}_{2}\right] \times 30 } & =[600+1000] \times 30 \mathrm{~Wh} \\
& =1600 \times 30=48000 \mathrm{~Wh} \\
& =48 \mathrm{kWh}
\end{aligned}
\]
Cost of using these electrical devices at the rate of ₹ $\displaystyle 8.00$ per kwh is
\(\displaystyle ₹ 48 \times 8=₹ 384\)More from Electricity
- (i) Consider the following electric circuit: Calculate the values of the following: (I) Total resistance of the circuit. (II) The total electric…2026
- A 2000 W heater has a resistance of about 25 Ω, whereas a 100 W bulb has a resistance of 500 Ω. When 220 V is applied on these, then which of the two…2024
- Show how you would connect three resistors each of resistance 6 Ω, so that the combination has a resistance of 9 Ω. Also justify your answer. OR In…2024
- In domestic electric circuits the wiring with 15 A current rating is for the electric devices which have2023
- Assertion: Electrons move from lower potential to higher potential in a conductor. Reason (R): A dry cell maintains electric potential difference…2024
- (i) State whether the currents and potential difference in all the bulbs will be same or different when in a circuit three bulbs of: same wattage are…2024
- Consider two lamps A and B of rating 50 W; 220 V and 25 W; 220 V respectively. Find the ratio of the resistances of the two lamps (i.e. R_A: R_B ).…2025
- Study the given electric circuit in which 2 A electric current is flowing between points X and Y. (i) Using the battery, key, voltmeter and ammeter…2026
CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.