Question

400,000 joules of energy is consumed by an electric heater in 400 s.

1. What is power of heater?
2. If the above energy is supplied at 200 V, what is the magnitude of current flowing through heater?
3. What is the resistance of the element of the heater?

Answer 1

(a) Given:

Energy (E) = 400,000 J

Time (t) = 400 s

Formula:

\[P=\frac{E}{t}\]

\[=\frac{400,000}{400}\]

\[={1,000}\text{\ W\ (or\ }1\text{\ kW)}\]

(b) Given:

Power (P) = 1000 W

Voltage (V) = 200 V

Formula:

\[P=V\times I\]

\[I=\frac{P}{V}\]

\[=\frac{1,000}{200}\]

\[={5}\text{\ A}\]

(c) Given:

Voltage (V) = 200 V

Current (I) = 5 A

Formula:

\[V=I\times R\]

\[R=\frac{V}{I}\]

\[=\frac{200}{5}\]

\[={40\ \Omega }\]