A heating element is marked 210 V, 630 W. The current drawn by the element and the resistance of the element when connected to 210 V DC mains would respectively be:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → $3 A, 70 \Omega$
Given,
V, Voltage of the heating element = 210 V
P, Power of the heating element = 630 W
Also,
$P=V×I$ [formula]
where,
I, current in the circuit
∴ $I=\frac{P}{V}=\frac{630}{210}$
$I=3A$
Now,
$P=V.\frac{V}{R}$ [V = IR : Ohm's law]
$⇒R=\frac{V^2}{P}=\frac{(210)^2}{630}$
$=70Ω$