Question

A potential difference of 250 Volts is applied across a resistance $1000\Omega$ in an electric iron. The current and heat energy produced in Joules in 12 sec will be:

• A. 0.25 A, 750 J
• B. 1.5 A, 75 J
• C. 2 A, 1000 J
• D. 0.25 A, 650 J

Answer 1

The correct option is A 0.25 A, 750 J

According to Ohm's law, $I=\frac{V}{R}$.
Hence, the current drawn by the electric iron is given as follows.
$I=\frac{V}{R}=\frac{250W}{1000V}=0.25A$

The electric power in watts associated with a complete electric circuit or a circuit component represents the rate at which energy is converted from the electrical energy of the moving charges to some other form, e.g., heat, mechanical energy, or energy stored in electric fields or magnetic fields. The power is given by the product of applied voltage and the electric current.
The heat produced or the energy dissipated by an appliance is given by the product of power and time taken in seconds. That is, $Q=Pt$.

Substituting $P=VI$, we get $Q=VI\times t=250V\times 0.25A\times 12s=750J$.