Yes, this is a problem given in class. I'm studying for a test and coudn't find an expression to 𝒗𝟏(𝒕). For me it seems like there is not enough data to do that. Can someone give me a direction?

A power supply V1 is connected to a load ZL by a wire of impedance 6,4 + j4,8 Ω, as shown in the following picture. Knowing that the angular frequency of the supply is 200 rad/s, the voltage on the load is 100 V (rms) and that it absorves 1000 W with a power factor of 0.8, determine:

(a) The voltage expression for the power supply 𝒗𝟏(𝒕);

Figure 2

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    \$\begingroup\$ Did you try and find the currrent, you know with V = IR or \$ \frac{V_L}{I_L} = Z_L \$ and P = I^2*Z and P = V^2*Z also \$PF = \frac{RealPower}{AppPower} \$ \$\endgroup\$ – Voltage Spike Nov 22 '16 at 0:14

Given it is a homework question I'm not going to give you a full answer, and you haven't shown any working or attempt, so I'll be even more vague. But you do have enough information to work out what input voltage is.

  • You know the real power and power factor of the load, so you can work out the apparent power (real+reactive) into the load.
  • You also know the voltage across the load (hint: you should know how to find peak from RMS) so knowing the apparent power you can work out the impedance of it.
  • Once you know the impedance you can work out the current.
  • Once you know the current you can work out the voltage across the wire impedance.
  • Once you know the voltage across the wire impedance you can work out the input voltage.
  • \$\begingroup\$ A full answer is not what I wanted, as I just wanted a direction. Thanks for pointing things out. I'll try to solve it now. \$\endgroup\$ – ddz Nov 22 '16 at 0:12

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