Volt-ampere (VA) is a unit that expresses both active power and reactive power in an electric circuit. VA is the product of voltage (V) and current (A) and is used to measure the power in a circuit.

Active power is the power actually used by an electrical device during operation and represents the energy consumed by electricity. For example, the active power used by the motor of an electric vacuum cleaner during operation is the electricity used to adjust the speed and height of the motor.

Reactive power is energy stored in a circuit and not used or produced during the operation of an electrical device. For example, the reactive power generated by a transformer during operation is the power generated by the difference in voltage and current in the transformer.

The VA unit is used to measure the total power requirement (active power and reactive power) of an electrical device because it expresses both active power and reactive power together. Therefore, the VA unit is an important unit, especially when designing and measuring electrical devices.

Volt and ampere are units of measurement used to specify the characteristics of an electric circuit.

Volt (V) is used to measure the electrical potential difference (or voltage) in a circuit. For example, if the electrical potential difference of a battery is 2 volts, this means that there is a 2 volt electrical potential difference between the two ends of the battery.

Ampere (A) is used to measure the electric current in a circuit. For example, the electric current in the motor of an electric vacuum cleaner might be 3 amperes while it is operating.

By using these together, you can measure the power of an electric circuit. For example, if the voltage and current of the motor of an electric vacuum cleaner are 2 volts and 3 amperes, respectively, the power of the motor would be 6 watts (volt * ampere = watt).