Question

The unit of electrical power is watt and 1 watt is the same as _________.
\[A.~~1\text{ }volt-ampere\]
\[B.~~1\text{ }volt/ampere\]
\[C.~~1\text{ }volt-coulomb\]
\[D.~~1\text{ }volt/coulomb\]

Answer 1

Hint: Try to understand the concept of electric power. Learn the formulas or equations involved and try to express the unit in different forms.

Complete step by step answer:
Electric power of an electric circuit can be defined as the rate of work done or the work done per unit time of the electric circuit. The unit of electrical power is watt.

Electric power can be given by the equation,

$\text{Electrical power = }\dfrac{\text{work done}}{time}$

Electrical work done (or energy) can be defined as the amount of energy required to move an electric charge Q through a potential difference V from one point to another point.

$E=QV$

Where E is the electrical energy or work done, Q is the charge and V is the potential difference or voltage
Putting this in the above equation,

$\text{electrical power, P = }\dfrac{QV}{t}$

Again, current can be defined as the flow of charge per unit time,

$I=\dfrac{Q}{t}$
So, we can write,
$P=V\dfrac{Q}{T}=VI$
$P=VI$

Where P is the electrical power, V is the voltage and I is the current
The unit of power is watt.

Again, in the above equation, the unit of V is volt and the unit of current is ampere.
So, we can write the unit of power as volt-ampere.
So, 1 watt = 1 volt-ampere

The correct option is (A).

Note: From ohm’s law we have V=IR, where R is the resistance.
So, we can also write the formula for electric power as,
$\begin{align}
  & P=VI \\
 & P=IR\times I \\
 & P={{I}^{2}}R \\
\end{align}$