Question

an electric iron of resistance of 20ohm takes a current of 5A calculate the heat developed in 30sec​

Answer 1

Given :

Resistance of the electric iron, R = 20Ω

Current , I = 5A

Time taken, t = 30sec

To find :

The heat developed in electric iron.

Solution :

here, we can use joules law of heating

According to joules law,

The heat produced in a resistor is directly proportional to

• the square of current for a given resistance ( H ∝ I²)
• the resistance for a given current (H ∝ R)
• the time for which the current flows through the resistor (H ∝ t).

In order words,

H = I²Rt

here,

• H denotes heat produced
• I denotes current
• R denotes resistance
• t denotes time

by substituting all the given values in the formula,

➠ H = I² × R × t

➠ H = (5)² × (20) × (30)

➠ H = 25 × 20 × 30

➠ H = 15000J${.}$

thus, the heat developed by the electric iron is 15000J.

Remember !

SI unit of Heat produced is joules (J)

Answer 2

$\huge\underline{\bf \orange{Aηsωeя :}}$

➠ H = I² × R × t

➠ H = (5)² × (20) × (30)

➠ H = 25 × 20 × 30

➠ H = 15000Joule. Ans.

Thus, the heat developed by the electric iron is 15000J.