Elektrina je všade okolo nás - od telefónu v tvojej... Show more
Slovenský jazyk
Angličtina
Matematika
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
6
•
Updated Mar 24, 2026
•
Elektrický prúd, napätie a odpor: Základy a meranie
1 / 9
Základy elektriny - prúd, napätie a odpor
Predstav si elektróny ako vodu v potrubí - táto analógia ti pomôže pochopiť všetky tri základné veličiny naraz.
Elektrický prúd (I) je vlastne tok elektrónov cez vodič, podobne ako množstvo vody tečúcej potrubím. Meria sa v ampéroch (A) a vypočíta sa vzorcom I = Q/t, kde Q je náboj a t je čas.
Elektrické napätie (U) funguje ako tlak vody v potrubí - bez neho by sa elektróny nepohybovali. Je to rozdiel elektrického potenciálu medzi dvoma bodmi a meria sa vo voltoch (V). Vzorec: U = W/Q.
Elektrický odpor (R) je ako zúženie v potrubí, ktoré brzdí tok vody. Každý materiál má iný odpor - meď má malý, guma veľký. Jednotka je ohm (Ω).
Tip: Tieto tri veličiny vždy fungujú spolu - ak zmením jednu, ovplyvním aj ostatné!
Ohmov zákon - kráľ všetkých vzorcov
Toto je najdôležitejší vzorec v elektrotechnike, ktorý spája všetky tri veličiny: U = R × I.
Z tohto základného vzorca si môžeš odvodiť všetky ostatné: I = U/R (keď hľadáš prúd) a R = U/I (keď hľadáš odpor).
Jednoduchý trik na zapamätanie: nakresli si trojuholník s U hore a I, R dole. Zakryj veličinu, ktorú hľadáš, a zostane ti správny vzorec.
Ohmov zákon hovorí, že prúd je priamo úmerný napätiu a nepriamo úmerný odporu. Inými slovami - čím vyššie napätie, tým väčší prúd. Čím väčší odpor, tým menší prúd.
Dôležité: Tento zákon platí len pre jednoduché rezistory, nie pre všetky elektronické súčiastky!
Meranie elektrických veličín
Každá veličina sa meria inak, takže pozor na správne zapojenie prístrojov!
Ampérmeter (meria prúd) sa zapája sériovo - prúd musí pretekať cez prístroj. Má malý vnútorný odpor, aby neovplyvňoval obvod.
Voltmeter (meria napätie) sa zapája paralelne k súčiastke, na ktorej meráme napätie. Má veľký vnútorný odpor, aby ním nepretekal zbytočne prúd.
Ohmometer (miera odpor) sa používa len na odpojených súčiastkach - nikdy nemeraj odpor pod napätím, zničíš prístroj!
Pamätaj si: Ampérmeter = sériovo, Voltmeter = paralelne, Ohmometer = odpojené!
Odpor vodiča a materiály
Odpor vodiča závisí od troch vecí: materiálu, dĺžky a hrúbky.
Vzorec pre odpor vodiča: R = ρ × l/S, kde ρ (ró) je špecifický odpor materiálu, l je dĺžka a S je plocha prierezu.
Logicky to dáva zmysel - dlhší vodič má väčší odpor, hrubší vodič má menší odpor. Meď vedie prúd lepšie ako železo, takže má menší špecifický odpor.
Zaujímavosť: odpor kovov rastie s teplotou. Preto sa žiarovky častejšie prepália pri zapínaní, keď sú studené a majú menší odpor.
Prakticky: Preto sa v domácnostiach používajú hrubé vodiče na silné spotrebiče - menší odpor znamená menšie straty energie!
Riešenie príkladov krok za krokom
Pri riešení úloh postupuj vždy systematicky: zapíš známe hodnoty, čo hľadáš, vyber vzorec a dosať.
Príklad: Žiarovka má odpor 240 Ω a je pripojená na 230 V. Aký prúd ňou preteká?
- Známe: R = 240 Ω, U = 230 V
- Hľadané: I = ?
- Vzorec: I = U/R = 230/240 = 0,96 A
Pozor na jednotky! Kilo (k) = 103, mili (m) = 10-3, mikro (μ) = 10-6. Vždy si prepočítaj na základné jednotky pred dosadením do vzorca.
Pri odpore vodiča nezabudni na mm² → m²: 1 mm² = 10-6 m².
Skúšková rada: Vždy si na konci skontroluj, či ti vyšiel rozumný výsledek - ak ti vyšiel prúd 1000 A v domácej žiarovke, niekde je chyba!
Dôležité tipy pre skúšku
Bezpečnosť: S elektrinou sa nehraj - vysoké napätie a prúdy môžu byť smrteľné. Vždy pracuj pod dozorom učiteľa.
Jednotky sú kľúčové: Najčastejšie chyby vznikajú pri prepočítavaní jednotiek. Nauč sa predpony naspamäť a vždy si ich prepočítaj.
Teplota ovplyvňuje odpor: U väčšiny kovov odpor s teplotou rastie, u polovodičov klesá. Toto môže byť otázka na skúške.
Ohmov zákon má limity: Platí len pre jednoduché rezistory, nie pre diódy, tranzistory či iné elektronické súčiastky.
Zapamätaj si tabuľku: Prúd-Ampérmeter-Sériovo, Napätie-Voltmeter-Paralelne, Odpor-Ohmometer-Odpojené.
Finálna rada: Nič sa neboj počítať - väčšina úloh používa len základný Ohmov zákon. Keď si osvojíš U = R × I, zvládneš všetko!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5
App Store
4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Elektrický prúd, napätie a odpor: Základy a meranie
Elektrina je všade okolo nás - od telefónu v tvojej ruke až po osvetlenie v triede. Aby si pochopil, ako fungujú všetky tieto zariadenia, musíš si osvojiť tri základné pojmy: elektrický prúd, napätie a odpor.
Základy elektriny - prúd, napätie a odpor
Predstav si elektróny ako vodu v potrubí - táto analógia ti pomôže pochopiť všetky tri základné veličiny naraz.
Elektrický prúd (I) je vlastne tok elektrónov cez vodič, podobne ako množstvo vody tečúcej potrubím. Meria sa v ampéroch (A) a vypočíta sa vzorcom I = Q/t, kde Q je náboj a t je čas.
Elektrické napätie (U) funguje ako tlak vody v potrubí - bez neho by sa elektróny nepohybovali. Je to rozdiel elektrického potenciálu medzi dvoma bodmi a meria sa vo voltoch (V). Vzorec: U = W/Q.
Elektrický odpor (R) je ako zúženie v potrubí, ktoré brzdí tok vody. Každý materiál má iný odpor - meď má malý, guma veľký. Jednotka je ohm (Ω).
Tip: Tieto tri veličiny vždy fungujú spolu - ak zmením jednu, ovplyvním aj ostatné!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Ohmov zákon - kráľ všetkých vzorcov
Toto je najdôležitejší vzorec v elektrotechnike, ktorý spája všetky tri veličiny: U = R × I.
Z tohto základného vzorca si môžeš odvodiť všetky ostatné: I = U/R (keď hľadáš prúd) a R = U/I (keď hľadáš odpor).
Jednoduchý trik na zapamätanie: nakresli si trojuholník s U hore a I, R dole. Zakryj veličinu, ktorú hľadáš, a zostane ti správny vzorec.
Ohmov zákon hovorí, že prúd je priamo úmerný napätiu a nepriamo úmerný odporu. Inými slovami - čím vyššie napätie, tým väčší prúd. Čím väčší odpor, tým menší prúd.
Dôležité: Tento zákon platí len pre jednoduché rezistory, nie pre všetky elektronické súčiastky!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Meranie elektrických veličín
Každá veličina sa meria inak, takže pozor na správne zapojenie prístrojov!
Ampérmeter (meria prúd) sa zapája sériovo - prúd musí pretekať cez prístroj. Má malý vnútorný odpor, aby neovplyvňoval obvod.
Voltmeter (meria napätie) sa zapája paralelne k súčiastke, na ktorej meráme napätie. Má veľký vnútorný odpor, aby ním nepretekal zbytočne prúd.
Ohmometer (miera odpor) sa používa len na odpojených súčiastkach - nikdy nemeraj odpor pod napätím, zničíš prístroj!
Pamätaj si: Ampérmeter = sériovo, Voltmeter = paralelne, Ohmometer = odpojené!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Odpor vodiča a materiály
Odpor vodiča závisí od troch vecí: materiálu, dĺžky a hrúbky.
Vzorec pre odpor vodiča: R = ρ × l/S, kde ρ (ró) je špecifický odpor materiálu, l je dĺžka a S je plocha prierezu.
Logicky to dáva zmysel - dlhší vodič má väčší odpor, hrubší vodič má menší odpor. Meď vedie prúd lepšie ako železo, takže má menší špecifický odpor.
Zaujímavosť: odpor kovov rastie s teplotou. Preto sa žiarovky častejšie prepália pri zapínaní, keď sú studené a majú menší odpor.
Prakticky: Preto sa v domácnostiach používajú hrubé vodiče na silné spotrebiče - menší odpor znamená menšie straty energie!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Riešenie príkladov krok za krokom
Pri riešení úloh postupuj vždy systematicky: zapíš známe hodnoty, čo hľadáš, vyber vzorec a dosať.
Príklad: Žiarovka má odpor 240 Ω a je pripojená na 230 V. Aký prúd ňou preteká?
- Známe: R = 240 Ω, U = 230 V
- Hľadané: I = ?
- Vzorec: I = U/R = 230/240 = 0,96 A
Pozor na jednotky! Kilo (k) = 103, mili (m) = 10-3, mikro (μ) = 10-6. Vždy si prepočítaj na základné jednotky pred dosadením do vzorca.
Pri odpore vodiča nezabudni na mm² → m²: 1 mm² = 10-6 m².
Skúšková rada: Vždy si na konci skontroluj, či ti vyšiel rozumný výsledek - ak ti vyšiel prúd 1000 A v domácej žiarovke, niekde je chyba!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Dôležité tipy pre skúšku
Bezpečnosť: S elektrinou sa nehraj - vysoké napätie a prúdy môžu byť smrteľné. Vždy pracuj pod dozorom učiteľa.
Jednotky sú kľúčové: Najčastejšie chyby vznikajú pri prepočítavaní jednotiek. Nauč sa predpony naspamäť a vždy si ich prepočítaj.
Teplota ovplyvňuje odpor: U väčšiny kovov odpor s teplotou rastie, u polovodičov klesá. Toto môže byť otázka na skúške.
Ohmov zákon má limity: Platí len pre jednoduché rezistory, nie pre diódy, tranzistory či iné elektronické súčiastky.
Zapamätaj si tabuľku: Prúd-Ampérmeter-Sériovo, Napätie-Voltmeter-Paralelne, Odpor-Ohmometer-Odpojené.
Finálna rada: Nič sa neboj počítať - väčšina úloh používa len základný Ohmov zákon. Keď si osvojíš U = R × I, zvládneš všetko!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
0
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Mock Exam
Quiz
Flashcards
Essay
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5
App Store
4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user