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Başvurunu YapElectricity basics - Power
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We have come to understand - with the help of earlier posts - that voltage drives current and that this current can do useful work for us. The amount of work that voltage and current can do is expressed in "power". The unit of power is watt/W, but when doing calculations "P" is used, taken from the first letter in the word "power". If on an electric appliance you find the markings "230V, 40W", it is to be understood that the appliance does useful work for us at the power of 40 watts if it is supplied the voltage 230 volts. If one does not supply the appliance with the prescribed voltage, it will not do useful work for us at the desired power.
Power is a product of voltage and current and can thus be calculated by voltage times current or V * I. The formulaic circle below summarizes both Ohm's Law - as presented in an earlier post - and how to calculate power:
Source: https://ashlandacademicscience.miraheze.org/w/index.php?curid=209 (2026-09-04)There is a great variety of electric appliances, for instance lightbulbs, heaters and motors, that do different kinds of useful work for us, for instance creating light, heat and motion.
Electric appliances:
Source: https://www.dreamstime.com/stock-illustration-home-electric-appliance-illustration-icon-set-hand-drawn-sketch-image92394788 (2026-09-04)In these cases, power is reaped in desirable ways. However, power can also be wasted in undesirable ways! Before current reaches the intended load - the lightbulb, the heater or the motor - it needs to be transported to the load through the conductor(s). Regardless of how efficient a conductor we use, there will always be some resistance, as explained earlier, which in turn will make the voltage and the current to be translated into heat, which is seldom useful: there is a loss of power. The same amount of current will reach the load, but the voltage is diminished through the loss of power. This drop in voltage is referred to as a "voltage drop".
The way to express how much energy is "used" during a certain period of time is given in "watt seconds/Ws" or "joules". However, it is more common and useful to express it in "kilowatt hours/kWh". For instance, a boiler that has a power output of 1000 watts and is used for 30 minutes will have used 1000 * 0,5 or 500 watt hours or 0,5 kilowatt hours.
To be continued: Meanwhile:
- This one was really hard to translate in my head. For instance, in Swedish the book litterally says "power is developed" instead of "power is generated". Is it confusing to say this in English? Similarly, is "loss of power" or "power loss" the correct term to express how power is lost during transport? Also, the watts and voltages that are written on electric appliences are, in Swedish, called "marked power/marked voltage". Are there equivalents in English?
- Is there any intuitive ways to visualize or imagine why current remains the same when a voltage drop occurs? If I understand correctly, current is expressed in ampere, which is a fixed amount of electrons passing through any one point in a circuit in one second. This current is driven by voltage. If resistance is constant, current increases when voltage is increased (I know nothing of the ratios). Wouldn't a voltage drop mean that less electrons are pushed through that one point in the circuit in one second?
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We have come to understand - with the help of earlier posts - that voltage drives current and that this current can do useful work for us. The amount of work that voltage and current can do is expressed in "power". The unit of power is watt/W, but when doing calculations "P" is used, taken from the first letter in the word "power". If on an electric appliance you find the markings "230V, 40W", it is to be understood that the appliance does useful work for us at the power of 40 watts if it is supplied the voltage 230 volts. If one does not supply the appliance with the prescribed voltage, it will not do useful work for us at the desired power.
Power is a product of voltage and current and can thus be calculated by voltage times current or V * I. The formulaic circle below summarizes both Ohm's Law - as presented in an earlier post - and how to calculate power:
Source: https://ashlandacademicscience.miraheze.org/w/index.php?curid=209 (2026-09-04)There is a great variety of electric appliances, for instance lightbulbs, heaters and motors, that do different kinds of useful work for us, for instance creating light, heat and motion.
Electric appliances:
Source: https://www.dreamstime.com/stock-illustration-home-electric-appliance-illustration-icon-set-hand-drawn-sketch-image92394788 (2026-09-04)In these cases, power is reaped in desirable ways. However, power can also be wasted in undesirable ways! Before current reaches the intended load - the lightbulb, the heater or the motor - it needs to be transported to the load through the conductor(s). Regardless of how efficient a conductor we use, there will always be some resistance, as explained earlier, which in turn will make the voltage and the current to be translated into heat, which is seldom useful: there is a loss of power. The same amount of current will reach the load, but the voltage is diminished through the loss of power. This drop in voltage is referred to as a "voltage drop".
The way to express how much energy is "used" during a certain period of time is given in "watt seconds/Ws" or "joules". However, it is more common and useful to express it in "kilowatt hours/kWh". For instance, a boiler that has a power output of 1000 watts and is used for 30 minutes will have used 1000 * 0,5 or 500 watt hours or 0,5 kilowatt hours.
To be continued: Meanwhile:
- This one was really hard to translate in my head. For instance, in Swedish the book litterally says "power is developed" instead of "power is generated". Is it confusing to say this in English? Similarly, is "loss of power" or "power loss" the correct term to express how power is lost during transport? Also, the watts and voltages that are written on electric appliences are, in Swedish, called "marked power/marked voltage". Are there equivalents in English?
- Is there any intuitive ways to visualize or imagine why current remains the same when a voltage drop occurs? If I understand correctly, current is expressed in ampere, which is a fixed amount of electrons passing through any one point in a circuit in one second. This current is driven by voltage. If resistance is constant, current increases when voltage is increased (I know nothing of the ratios). Wouldn't a voltage drop mean that less electrons are pushed through that one point in the circuit in one second?
Im an American electrician, I can help a little. Great series btw, ive been following these posts and youve done a solid job of explaining electrical basics thus far.
in Swedish the book litterally says "power is developed" instead of "power is generated". Is it confusing to say this in English?
A little, we dont use the word "develop" in this context although it would mean functionally the same thing.
Similarly, is "loss of power" or "power loss" the correct term to express how power is lost during transport
Yup, thats how we describe voltage drop. For anyone reading this who's curious, this is why you have to upsize your conductors for every 100' between source and load. For instance, I have a 120V, 20A load 110' from my panel, therefore I'll pull #10AWG wire instead of the usual #12. This is also why, if your house sits waaay back on your property away from the road and pole, you'll need the power company to set a transformer between the pole and your meter. Transformers generate power in a secondary isolated circuit and can compensate for the loss of power over distance.
Also, the watts and voltages that are written on electric appliences are, in Swedish, called "marked power/marked voltage". Are there equivalents in English?
Not on typical home appliances, you might see something like this in specific industrial settings though I imagine. Appliances will typically have their requirements listed in Full Load Amps (FLA), meaning the maximum amount of current the device will need when it's running. If there's a larger motor in the device, you may also see a rating for starting current - how much energy is needed to overcome inertia and get the motor spinning. This can be much higher than the FLA, which is why they'll often have a start capacitor to provide the extra power.
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Im an American electrician, I can help a little. Great series btw, ive been following these posts and youve done a solid job of explaining electrical basics thus far.
in Swedish the book litterally says "power is developed" instead of "power is generated". Is it confusing to say this in English?
A little, we dont use the word "develop" in this context although it would mean functionally the same thing.
Similarly, is "loss of power" or "power loss" the correct term to express how power is lost during transport
Yup, thats how we describe voltage drop. For anyone reading this who's curious, this is why you have to upsize your conductors for every 100' between source and load. For instance, I have a 120V, 20A load 110' from my panel, therefore I'll pull #10AWG wire instead of the usual #12. This is also why, if your house sits waaay back on your property away from the road and pole, you'll need the power company to set a transformer between the pole and your meter. Transformers generate power in a secondary isolated circuit and can compensate for the loss of power over distance.
Also, the watts and voltages that are written on electric appliences are, in Swedish, called "marked power/marked voltage". Are there equivalents in English?
Not on typical home appliances, you might see something like this in specific industrial settings though I imagine. Appliances will typically have their requirements listed in Full Load Amps (FLA), meaning the maximum amount of current the device will need when it's running. If there's a larger motor in the device, you may also see a rating for starting current - how much energy is needed to overcome inertia and get the motor spinning. This can be much higher than the FLA, which is why they'll often have a start capacitor to provide the extra power.
Thank you so much for sharing your knowledge and expertise! I am truly humbled! ❤️ For instance, this
this is why you have to upsize your conductors for every 100’ between source and load. For instance, I have a 120V, 20A load 110’ from my panel, therefore I’ll pull #10AWG wire instead of the usual #12.
was such a nice addition to what I just learned in my books!Also, this
Transformers generate power in a secondary isolated circuit and can compensate for the loss of power over distance.
made me view transformers in a whole new light: they are like repeaters and routers if they also have a, say, rectifier! Right? A little networking comparison. 😁 -
Thank you so much for sharing your knowledge and expertise! I am truly humbled! ❤️ For instance, this
this is why you have to upsize your conductors for every 100’ between source and load. For instance, I have a 120V, 20A load 110’ from my panel, therefore I’ll pull #10AWG wire instead of the usual #12.
was such a nice addition to what I just learned in my books!Also, this
Transformers generate power in a secondary isolated circuit and can compensate for the loss of power over distance.
made me view transformers in a whole new light: they are like repeaters and routers if they also have a, say, rectifier! Right? A little networking comparison. 😁My pleasure! I love teaching and dont get to do it often haha.
Sadly I know very little about networking. I tend to think of or explain transformers in this context like adding an extra pump to a water line going uphill - the source pump becomes less effective as you fight against gravity (resistance), adding another pump along the way helps overcome that and keeps the first pump from over-working.
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With your input, this post could be even better 💗
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