I have a ceiling fan that consumes 90-watt energy. If I have a solar panel that generates 500-watt energy, then how does a 90-watt fan consumes only what it requires from a 500-watt solar panel.?
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1\$\begingroup\$ when you apply voltage to a load it consumes some current and power consumed is voltage times current and in your case it is 90 W. Your solar cell is of 500 watt. This means that if that solar panel applies 50 V to fan that that solar panel can apply a maximum of 10 A of current. Notice that it is maximum and your load need not to draw 10 A. \$\endgroup\$– Sanmveg sainiCommented Oct 1, 2020 at 13:47
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1\$\begingroup\$ How does an open circuit consume 500 watts when there is nothing connected. How could switches ever work if the potential power supplied to one side naturally crossed over to the other side. \$\endgroup\$– Andy akaCommented Oct 1, 2020 at 13:52
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\$\begingroup\$ no, no... 500 w means panel's expected power production under ideal condition and the numbers that I mentioned were just random. @Andyaka It is totally fine If you point out any mistake, I will delete and change it accordingly. \$\endgroup\$– Sanmveg sainiCommented Oct 1, 2020 at 14:03
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\$\begingroup\$ @Sanmveg A solar panel cant just provide any arbitrary voltage and current whose product is its power rating. So unless you know 50 V is the max power point the panel will provide less than 10 A max. \$\endgroup\$– MattCommented Oct 1, 2020 at 15:19
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1\$\begingroup\$ @KurioZ7: Thought experiment. My house is connected to the national grid. How does an 8 W LED lamp connected to the mains not consume all 5 GW of the national grid? \$\endgroup\$– TransistorCommented Oct 1, 2020 at 16:40
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A PV panel generates voltage like a generator by separating positive and negative charges. It will do so in the moment when it is exposed to light. When the circuit between the different potentials is open-circuited, no current can flow, the PV panel will produce voltage but no power. Its just unused. So e.g. your panel produces 100V, then 100V*0A=0W.
You may use any fraction of energy you want from an electrical source. This is always the case if you do not consume all the power which can be generated. But as soon as a consumer demands the provided power generated, it will be used.
This is why you can use the same batteries in an energy saving remote control and a high power torch. Any consumer "tress" to sink the current needed, and if the source can deliver it it's OK. If a consumer does not need all the power a source can deliver, it will just work and leave some energy for other consumers.
PS: In an AC power grid with rotating generators, if not all power is needed, the generators will spin faster and the frequency will rise. The plant will then reduce power generated by the turbines, so the generator reduces rotation speed again. The same happens if too many consumers demand power at once: frequency drops, and the power plant will increase power generated by the turbines so the generator rotates faster again.
