Understanding electric circuits is crucial for GCSE Physics, and it's... Show more
Physics
SociologySign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
8
0
E
Eva
26/11/2025
Physics
physics electricity
357
•
26 Nov 2025
•
Understanding Electricity in Physics
E
Eva
@eva_xxlp5
1 / 9
Current and Circuit Symbols
Current is simply the flow of electric charge, and it only flows when there's a complete circuit with potential difference (voltage) to push it around. Think of voltage as the driving force - like water pressure in pipes - whilst resistance acts like obstacles that slow the flow down.
In series circuits, current stays the same everywhere, but in parallel circuits it splits up. The key relationship to remember is that higher resistance means lower current flows through that component.
You'll need to recognise circuit symbols like lamps, switches, fuses, and measuring devices. Ammeters measure current and go in series, whilst voltmeters measure potential difference and connect in parallel.
Quick Formula: Charge flow = Current × Time . This tells you how much charge passes through a circuit over time.
Measuring Resistance - Required Practical
This practical investigation shows how wire length affects resistance. You'll use crocodile clips to test different lengths of wire, measuring current with an ammeter (in series) and potential difference with a voltmeter (in parallel).
The method involves moving clips along a ruler at 10cm intervals, recording current and voltage each time. Always open the switch between readings to prevent the wire heating up and affecting results.
When you plot resistance against wire length, you should get a straight line through the origin. This proves resistance is directly proportional to length - longer wires have greater resistance.
Key Equation: Potential difference = Current × Resistance . Use your current and voltage readings to calculate resistance for each wire length.
Current-Voltage Characteristics
Different components behave differently when current flows through them. Ohmic conductors like fixed resistors follow Ohm's law - their resistance stays constant, so current is directly proportional to voltage.
Filament bulbs behave differently because as current increases, the filament heats up and resistance increases. This creates a curved graph that gets shallower at higher currents.
Diodes only allow current to flow in one direction. They have very high resistance in the reverse direction, creating a distinctive one-sided graph.
Required Practical Tip: Use a variable resistor to change current and voltage readings. Always take repeat readings and reverse the cell connections to test both directions.
Resistance Components
Light Dependent Resistors (LDRs) change resistance based on light intensity. In bright light, resistance falls dramatically, whilst in darkness it's highest. You'll find these in automatic night lights, street lamps, and burglar detectors.
Thermistors are temperature-dependent resistors. In hot conditions, resistance drops, but in cold conditions it increases significantly. They're perfect for temperature sensors in car engines and electronic thermostats.
Both components are examples of how resistance can be useful for sensing environmental changes. Understanding their behaviour helps explain how automatic systems work in everyday technology.
Memory Tip: LDR = Light Down, Resistance down. Thermistor = Temperature up, Resistance down.
Series Circuits
In series circuits, components connect end-to-end in a single loop. Current is identical everywhere, but potential difference gets shared between components. The total voltage always adds up to equal the power supply voltage.
If one component breaks or gets removed, the entire circuit stops working - like old Christmas lights that all went out when one bulb failed.
Total resistance is simply the sum of all individual resistances . Adding more resistors increases total resistance, which reduces current throughout the circuit.
Key Point: The component with the biggest resistance gets the biggest share of the voltage. This is why dim bulbs in series circuits often have high resistance.
Parallel Circuits
Parallel circuits connect each component separately to the power supply's positive and negative terminals. Every component gets the full source voltage, making identical bulbs equally bright.
Current splits at junctions and rejoins later. The total current equals the sum of currents through each branch. If components are identical, current divides equally between them.
Adding resistors in parallel actually reduces total resistance because current has more paths to follow. This increases total current whilst maintaining the same voltage across each component.
Real-world Application: Your home uses parallel circuits so lights and appliances work independently - when your bedroom light breaks, the kitchen light still works perfectly.
Mains Electricity and Safety
The UK mains supply provides alternating current (AC) at 230V and 50Hz frequency. Unlike batteries that provide direct current (DC), AC constantly changes direction.
Three-pin plugs contain live wire (brown, brings voltage in), neutral wire (blue, completes circuit), and earth wire . The live wire causes electric shocks because your body is at 0V.
Fuses protect circuits by melting when current gets too high. Choose a fuse rating just above the normal operating current - a 4A appliance needs a 5A fuse, not a 13A one.
Safety Rule: Never touch the live wire! The 230V potential difference across your body can cause dangerous current flow.
Electrical Power Calculations
Power tells you how quickly energy gets transferred, measured in watts. You'll use three key equations: P = VI , E = Pt , and E = QV .
For calculation questions, always convert units properly - kilowatts to watts, minutes to seconds. Work systematically through the steps and check your significant figures.
These equations help you understand running costs, energy efficiency, and why some appliances use more electricity than others.
Exam Tip: Power calculations often involve unit conversions. A 1.5kW kettle = 1500W, and 5 minutes = 300 seconds. Get the units right first!
The National Grid
The national grid is the UK's electricity distribution system connecting power stations to homes and businesses through cables and transformers. It efficiently transfers power anywhere it's needed across the country.
High voltage transmission is crucial for efficiency. Using high voltage and low current minimises energy waste from heating in cables. Step-up transformers increase voltage for transmission, whilst step-down transformers reduce it safely for homes.
Power stations continuously adjust output to match changing demand throughout the day. They predict increases when people wake up, return from work, or during major TV events.
Key Concept: High voltage = low current = less energy wasted as heat. This makes the national grid incredibly efficient for long-distance power transmission.
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: Resistance
Most popular content in Physics
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
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 THE SCHOOLGPT. 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 THE SCHOOLGPT. 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
Understanding Electricity in Physics
E
Eva
@eva_xxlp5
Understanding electric circuits is crucial for GCSE Physics, and it's everywhere in daily life - from your phone charger to how electricity reaches your home. This topic covers current flow, resistance, circuit types, and the national grid system that powers... Show more
Current and Circuit Symbols
Current is simply the flow of electric charge, and it only flows when there's a complete circuit with potential difference (voltage) to push it around. Think of voltage as the driving force - like water pressure in pipes - whilst resistance acts like obstacles that slow the flow down.
In series circuits, current stays the same everywhere, but in parallel circuits it splits up. The key relationship to remember is that higher resistance means lower current flows through that component.
You'll need to recognise circuit symbols like lamps, switches, fuses, and measuring devices. Ammeters measure current and go in series, whilst voltmeters measure potential difference and connect in parallel.
Quick Formula: Charge flow = Current × Time . This tells you how much charge passes through a circuit over time.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Measuring Resistance - Required Practical
This practical investigation shows how wire length affects resistance. You'll use crocodile clips to test different lengths of wire, measuring current with an ammeter (in series) and potential difference with a voltmeter (in parallel).
The method involves moving clips along a ruler at 10cm intervals, recording current and voltage each time. Always open the switch between readings to prevent the wire heating up and affecting results.
When you plot resistance against wire length, you should get a straight line through the origin. This proves resistance is directly proportional to length - longer wires have greater resistance.
Key Equation: Potential difference = Current × Resistance . Use your current and voltage readings to calculate resistance for each wire length.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Current-Voltage Characteristics
Different components behave differently when current flows through them. Ohmic conductors like fixed resistors follow Ohm's law - their resistance stays constant, so current is directly proportional to voltage.
Filament bulbs behave differently because as current increases, the filament heats up and resistance increases. This creates a curved graph that gets shallower at higher currents.
Diodes only allow current to flow in one direction. They have very high resistance in the reverse direction, creating a distinctive one-sided graph.
Required Practical Tip: Use a variable resistor to change current and voltage readings. Always take repeat readings and reverse the cell connections to test both directions.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Resistance Components
Light Dependent Resistors (LDRs) change resistance based on light intensity. In bright light, resistance falls dramatically, whilst in darkness it's highest. You'll find these in automatic night lights, street lamps, and burglar detectors.
Thermistors are temperature-dependent resistors. In hot conditions, resistance drops, but in cold conditions it increases significantly. They're perfect for temperature sensors in car engines and electronic thermostats.
Both components are examples of how resistance can be useful for sensing environmental changes. Understanding their behaviour helps explain how automatic systems work in everyday technology.
Memory Tip: LDR = Light Down, Resistance down. Thermistor = Temperature up, Resistance down.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Series Circuits
In series circuits, components connect end-to-end in a single loop. Current is identical everywhere, but potential difference gets shared between components. The total voltage always adds up to equal the power supply voltage.
If one component breaks or gets removed, the entire circuit stops working - like old Christmas lights that all went out when one bulb failed.
Total resistance is simply the sum of all individual resistances . Adding more resistors increases total resistance, which reduces current throughout the circuit.
Key Point: The component with the biggest resistance gets the biggest share of the voltage. This is why dim bulbs in series circuits often have high resistance.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Parallel Circuits
Parallel circuits connect each component separately to the power supply's positive and negative terminals. Every component gets the full source voltage, making identical bulbs equally bright.
Current splits at junctions and rejoins later. The total current equals the sum of currents through each branch. If components are identical, current divides equally between them.
Adding resistors in parallel actually reduces total resistance because current has more paths to follow. This increases total current whilst maintaining the same voltage across each component.
Real-world Application: Your home uses parallel circuits so lights and appliances work independently - when your bedroom light breaks, the kitchen light still works perfectly.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Mains Electricity and Safety
The UK mains supply provides alternating current (AC) at 230V and 50Hz frequency. Unlike batteries that provide direct current (DC), AC constantly changes direction.
Three-pin plugs contain live wire (brown, brings voltage in), neutral wire (blue, completes circuit), and earth wire . The live wire causes electric shocks because your body is at 0V.
Fuses protect circuits by melting when current gets too high. Choose a fuse rating just above the normal operating current - a 4A appliance needs a 5A fuse, not a 13A one.
Safety Rule: Never touch the live wire! The 230V potential difference across your body can cause dangerous current flow.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Electrical Power Calculations
Power tells you how quickly energy gets transferred, measured in watts. You'll use three key equations: P = VI , E = Pt , and E = QV .
For calculation questions, always convert units properly - kilowatts to watts, minutes to seconds. Work systematically through the steps and check your significant figures.
These equations help you understand running costs, energy efficiency, and why some appliances use more electricity than others.
Exam Tip: Power calculations often involve unit conversions. A 1.5kW kettle = 1500W, and 5 minutes = 300 seconds. Get the units right first!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The National Grid
The national grid is the UK's electricity distribution system connecting power stations to homes and businesses through cables and transformers. It efficiently transfers power anywhere it's needed across the country.
High voltage transmission is crucial for efficiency. Using high voltage and low current minimises energy waste from heating in cables. Step-up transformers increase voltage for transmission, whilst step-down transformers reduce it safely for homes.
Power stations continuously adjust output to match changing demand throughout the day. They predict increases when people wake up, return from work, or during major TV events.
Key Concept: High voltage = low current = less energy wasted as heat. This makes the national grid incredibly efficient for long-distance power transmission.
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.
8
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: Resistance
Most popular content in Physics
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
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 THE SCHOOLGPT. 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 THE SCHOOLGPT. 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