Question

A heater coil is rated $100$W, $200$V. It is cut into two identical parts. Both parts are connected together in parallel, to the same source of $200$V. The energy liberated per second in the new combination is?

• A. $100$J
• B. $200$J
• C. $300$J
• D. $400$J

Answer 1

Answer: (D)

$400$J

$P=100W$

$V=200V$

$P=\frac{V^2}{R}$

$R=\frac{(200{)}^2}{400}=100\Omega$

Net Resistance:

$\frac{1}{R_t}=\frac{1}{R^{\prime }}+\frac{1}{R^{\prime }}=\frac{2}{R^{\prime }}$

$⟹R_t=\frac{R^{\prime }}{2}=\frac{200}{2}=100\Omega$

Net Power$=P=\frac{V^2}{RT}=\frac{40000}{100}=400J$