Question

If the resistance of two soldering irons working in 250 V are 500 $$\Omega$$ and 750 $$\Omega$$.
a. Calculate which one of these will carry more current.
b. Find out which soldering iron has more power.
c. Calculate the heat produced in 5 minutes in the soldering iron having resistance 750 $$\Omega$$.

Answer 1

a. $$I= \dfrac{V}{R}$$
Current through 500 $$\Omega$$
$$I= \dfrac{250\ V}{500\ \Omega}= \dfrac12 \ A$$
Current through 750 $$\Omega$$
$$I=\dfrac{250 \ V}{750 \ \Omega}= \dfrac13 \ A$$
b. Soldering iron has less resistance
c. $$H= I^2Rt $$ Or $$H= \dfrac{V^2 t}{R}$$
$$H= \dfrac{250^2 \times 300}{750} = 25000 \ J$$