Question

An electric iron of resistance 20 Ω takes a current of 5A. Calculate the heat developed in 30s ?

Answer 1

Explanation:

Heat is equal to I²RT.

Therefore heat is equal to 1500 J

Answer 2

Given :-

Resistance of the electric iron = 20 Ω

Current of the electric iron = 5 A

Time taken by the electric iron to develop heat = 30 sec

To Find :-

The heat developed by the electric iron is 30 sec.

Analysis :-

Firstly find the voltage by substituting the given values such that voltage is equal to current multiplied by resistance.

Then substituting the values we got such that heat is equal to voltage multiplied by current into time.

Solution :-

We know that,

• v = Voltage
• i  = Current
• r = Resistance
• t = Time
• h = Heat

Using the formula,

$\underline{\boxed{\sf Voltage=Current \times Resistance}}$

Given that,

Current (i) = 5 A

Resistance (r) = 20 Ω

Substituting their values,

⇒ v = ir

⇒ v = 5 × 20

⇒ v = 100 V

Using the formula,

$\underline{\boxed{\sf Heat=Voltage \times Current \times Time}}$

Given that,

Voltage (v) = 100 V

Current (i) = 5 A

Time (t) = 30 sec

Substituting their values,

⇒ h = 100 × 5 × 30

⇒ h = 15000 J

⇒ h = 1.5 × 10⁴ J

Therefore, the heat developed by the electric iron is 1.5 × 10⁴ J.