Question

27) A 2 kW heater, a 400 W TV and three 150 W lamps are all switched on from 6 a.m. to 10
p.m. What is the total cost at Rs. 8.50 per kWh ?
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Answer 1

Given :-

Power of the heater = 2 kW

Time taken = 4 hours

Power of the TV = 400 W

Power of the lamp = 150 W

To Find :-

The total cost at Rs. 8.50 per kWh.

Solution :-

We know that,

• e = Energy
• p = Power
• t = Time

Total power,

Given that,

p₁ = 2 kW

p₂ = 400 W = 0.4 kW

p₃ = 150 W = 0.15 kW

Substituting their values,

⇒ p₁ + p₂ + p₃

⇒ 2 + 0.4 + 0.15

⇒ 2.55 kW

Using the formula,

$\underline{\boxed{\sf Energy=Power \times Time}}$

Given that,

Power (p) = 2.55 kW

Time (t) = 4 hours

Substituting their values,

⇒ e = p × t

⇒ e = 2.55 × 4

⇒ e = 10.2 kWh

According to the question,

Given that,

Cost per kWh = Rs. 8.50

Substituting their values,

⇒ 10.5 × 8.50

⇒ Rs. 86.7

Therefore, the total cost at Rs. 8.50 per kWh is 86.7.

Answer 2

Answer:

GIVEN:

PH=2KW,PTV=0.4KW,PLAMPS=3×150= 0.45KW

FIRST FORMULA OF ENERGY

IS ENERGY = POWER ×TIME

SO, EH= 2×16=32KWH , ETV= 0.4×16=6.4kwh, 0.45×16=7.2kwh TE = 45.6kwh so simply multiply 45.6 kwh to 8.50 = 387.6 ₹