Question

An electric iron of resistance $20\Omega$ takes a current of $5A$. Calculate the heat developed in $30s.$

Answer 1

Step 1: Given data

The current passes through the resistance is, $I=5A$ .

The value of the resistance is $R=20\Omega$.

Given time for heat development is $T=30seconds.$

Step 2: Joule's law of heating

1. Joule's law states that when a current I is flowing in a conductor of resistance R for a time T sec, then the produced heat on the conductor is directly proportional to the square of the electric current.
2. Joule's law is defined by the form, $H=I^{2}RT$ , where, H is the produced heat on the conductor.

Step 3: Calculation of heat

Now applying Joule's law,

$$\begin{gathered} H=I^{2}RT=5^2\times 20\times 30 \\ orH=15000Joule. \end{gathered}$$

Therefore, the heat developed by the iron in $30s$ is $15000joule.$