Question

Determine the power dissipated by the element of an electric fire of resistance 20 ohm when a current of 10A flows through it. If the fire is on for 6 hours determine the energy used and the cost if 1 unit of unit of electricity costa 7p​

Answer 1

Resistance = 20 ohm

current = 10 A

power = i^2R

power =10×10×20

power = 2000w

time = 6h

electric energy consumed = 2kw×6=12kwh or 12 unit

1unit= 7p

12 unit = 12×7 = 84p

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Answer 2

Answer:

Explanation:

Given :

To determine the power dissipated by the element of an electric fire of resistance 20 Ω when a current of 10A flows through it. If the fire is on for 6 hours determine the energy used and the cost if 1 unit of unit of electricity cost 7p.​

Solution :

We know that,

Power (P) = VI = (IR)I = I²R

We have,

I = 10 A

R = 20 Ω

⇒ P = (10²) × 20 = 100 × 20 = 2000 W

The energy dissipated by a fire of 6 hours = Heat energy dissipated by the fire = VIT = (IR)IT = I²RT, where time is in seconds,.

Time = 6 hours = 6 × 60 × 60 = 21600 seconds

⇒ H = I²RT = (10)² × 20 ×  21600 = 100 × 20 × 21600 = 53200000

= 4.32 × 10⁷ J = 12 × (3.6 × 10⁶) = 12 units

The cost of electricity per hour = 7p

⇒ Tota cost = Power(in kw) × Time(in hours) × Cost per hour = 2 × 6 × 7p = 84 p