Calculating Heat Flow in Electric Iron

The problem asks for the heat generated by an electric iron given its resistance, current, and the time duration.

Given Data:

• Resistance, $R$ = 20 ohm
• Current, $I$ = 5 A
• Time, $t$ = 30 s

Formula Used:

The heat generated by an electrical appliance is calculated using Joule's law of heating:

$H = I^2 R t$

Where:

• $H$ is the heat generated (in Joules, J)
• $I$ is the current flowing (in Amperes, A)
• $R$ is the resistance (in Ohms, $\Omega$)
• $t$ is the time (in Seconds, s)

Calculation:

Substitute the given values into the formula:

$H = (5\text{ A})^2 \times (20\ \Omega) \times (30\text{ s})$

First, calculate the square of the current:

$I^2 = (5)^2 = 25\text{ A}^2$

Now, multiply this by the resistance and time:

$H = 25\text{ A}^2 \times 20\ \Omega \times 30\text{ s}$

$H = 500 \times 30\text{ J}$

$H = 15000\text{ J}$

Expressing this in scientific notation:

$H = 1.5 \times 10^4\text{ J}$

Result:

The heat flow in 30 seconds is $1.5 \times 10^4\text{ J}$.