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This question is from an exam to this year official university access tests (see here, in Catalan):

In Catalan:

Connectem en paral·lel una reactància capacitiva de 100 Ω i una reactància inductiva de 50 Ω. El conjunt s’alimenta d’una xarxa de 100 V. Quina és la potència reactiva consumida pel conjunt?

Translation:

We connect in parallel one capacitive reactancy of 100 Ω and one inductive reactor of 50 Ω. The set feeds on a net of 100 v. What is the reactive power consumed by the set?

Possible answers was 0 var, 100 var, 200 var and -100 var, being correct one 100 var.

My question is: when we talk about reactive power, we can talk about power consumption?

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    \$\begingroup\$ Interesting question. We can't say "what is the power dissipated" obviously, so maybe "consumed" is marginally better? I would say "what is the apparent power drawn by the circuit?" Or something like that. ¡Bona sort! \$\endgroup\$ – John D Aug 14 '17 at 20:38
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We should probably not say "consumed." A terminology system that has been proposed and followed by some people states:

When the Reactive Power (Vars) flow from the “SOURCE” through the metering point and into the “LOAD” we say the Reactive Power (Vars) are being DELIVERED. Therefore when the Reactive Power is being supplied by the “SOURCE” into the load it will be referred to as Delivered Reactive Power (Vars) and have a positive sign.

When the Reactive Power (Vars) flow from the “LOAD” through the metering point and into the “SOURCE” we say the Reactive Power (Vars) are being RECEIVED. Therefore when the Reactive Power is being supplied by the “LOAD” into the source it will be referred to as Received Reactive Power (Vars) and have a negative sign.

In this system, inductive volt-amperes received by the load have a positive sign. If the load is capacitive, the volt-amperes have a negative sign.

Note that negative power factor should not be used in conjunction with reactive power flow. However real power returned by the load to the source will cause the power factor to be negative.

This system of terminology is described in more detail in the source of the above quotation: Understanding Power Flow and Naming Conventions In Bi-directional Metering Applications By Michael Bearden


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  • \$\begingroup\$ Interesting that delivered/received is defined from the point of view of the source, not of the load. \$\endgroup\$ – pasaba por aqui Aug 15 '17 at 8:08

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