🕷️ Crawler Inspector

URL Lookup

Direct Parameter Lookup

Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 132 (from laksa164)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa132.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/10","crawl_time":1760661420,"first_indexed_time":0,"http_code":200,"src_unparsed":"uk,co,bbc!www,\/bitesize\/guides\/zk37hyc\/revision\/10 s443","src_root_hash":"2272746388958996332","history_drop_reason":null,"meta_title":"Calculating the value of the series resistor - Practical electrical and electronic circuits - National 5 Physics Revision - BBC Bitesize","meta_descriptions":["In National 5 Physics examine the current and voltage in series and parallel circuits to formulate rules and determine unknown values."],"attrs_boilerpipe_text":"To use one of these LEDs in a circuit powered by a \\(6V\\)  battery close battery A chemical supply of electrical energy. For example, common battery voltages include 1.5 V and 9 V. , we would calculate the required series resistance as follows.","attrs_markdown":"[BBC Homepage](https:\/\/www.bbc.com\/)\n\n- [Skip to content](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/10#main-heading)\n- [Accessibility Help](https:\/\/www.bbc.co.uk\/accessibility\/)\n\n- [Your account](https:\/\/account.bbc.com\/account?lang=en-GB&ptrt=https%3A%2F%2Fwww.bbc.co.uk%2Fbitesize%2Fguides%2Fzk37hyc%2Frevision%2F10)\n\n- [Home](https:\/\/www.bbc.com\/)\n- [News](https:\/\/www.bbc.com\/news)\n- [Sport](https:\/\/www.bbc.com\/sport)\n- [Earth](https:\/\/www.bbc.com\/future\/earth)\n- [Reel](https:\/\/www.bbc.com\/reel)\n- [Worklife](https:\/\/www.bbc.com\/worklife)\n- [Travel](https:\/\/www.bbc.com\/travel)\n- [Culture](https:\/\/www.bbc.com\/culture)\n- [Future](https:\/\/www.bbc.com\/future)\n- [Music](https:\/\/www.bbc.com\/culture\/music)\n- [TV](https:\/\/www.bbc.co.uk\/schedules\/p00fzl9m)\n- [Weather](https:\/\/www.bbc.com\/weather)\n- [Sounds](https:\/\/www.bbc.co.uk\/sounds)\n- [More menu](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/10#global-navigation-more-menu)\n\n[More menu](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/10#global-navigation-more-menu)\n\n[Search Bitesize](https:\/\/www.bbc.co.uk\/bitesize\/search?d=BITESIZE)\n\n- [Home](https:\/\/www.bbc.com\/)\n- [News](https:\/\/www.bbc.com\/news)\n- [Sport](https:\/\/www.bbc.com\/sport)\n- [Earth](https:\/\/www.bbc.com\/future\/earth)\n- [Reel](https:\/\/www.bbc.com\/reel)\n- [Worklife](https:\/\/www.bbc.com\/worklife)\n- [Travel](https:\/\/www.bbc.com\/travel)\n- [Culture](https:\/\/www.bbc.com\/culture)\n- [Future](https:\/\/www.bbc.com\/future)\n- [Music](https:\/\/www.bbc.com\/culture\/music)\n- [TV](https:\/\/www.bbc.co.uk\/schedules\/p00fzl9m)\n- [Weather](https:\/\/www.bbc.com\/weather)\n- [Sounds](https:\/\/www.bbc.co.uk\/sounds)\n\n[Close menu](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/10#more-menu-button)\n\n[Bitesize](https:\/\/www.bbc.co.uk\/bitesize)\n\n[Menu](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/10#product-navigation-menu)\n\n- [Home](https:\/\/www.bbc.co.uk\/bitesize)\n- [Learn](https:\/\/www.bbc.co.uk\/bitesize\/learn)\n- [Study support](https:\/\/www.bbc.co.uk\/bitesize\/study-support)\n- [Careers](https:\/\/www.bbc.co.uk\/bitesize\/careers)\n- [Teachers](https:\/\/www.bbc.co.uk\/teach)\n- [Parents](https:\/\/www.bbc.co.uk\/bitesize\/parents)\n- [Trending](https:\/\/www.bbc.co.uk\/bitesize\/trending)\n- [My Bitesize](https:\/\/www.bbc.co.uk\/bitesize\/my)\n\n[More](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/10#product-navigation-more-menu)\n\n**England**\n\n- [Early years](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zt6svwx)\n- [KS1](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z3g4d2p)\n- [KS2](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zbr9wmn)\n- [KS3](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z4kw2hv)\n- [GCSE](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z98jmp3)\n- [Functional Skills](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zvhtng8)\n\n**Northern Ireland**\n\n- [Foundation Stage](https:\/\/www.bbc.co.uk\/bitesize\/levels\/znyh7nb)\n- [KS1](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zcwyp4j)\n- [KS2](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zjmj92p)\n- [KS3](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z3hbg7h)\n- [GCSE](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z98jmp3)\n\n**Scotland**\n\n- [Early Level](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zf7hgwx)\n- [1st Level](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zgckjxs)\n- [2nd Level](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zr48q6f)\n- [3rd Level](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zy4qn39)\n- [4th Level](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zvk2fg8)\n- [National 4](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zp3d7ty)\n- [National 5](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z6gw2hv)\n- [Higher](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zkdqxnb)\n- [Core Skills](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z66jhbk)\n- [An Tràth Ìre](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zggh6g8)\n- [A' Chiad Ìre](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zk3xy9q)\n- [An Dàrna Ìre](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z4y2scw)\n- [3mh ìre](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zmd346f)\n- [4mh ìre](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zxwb9ty)\n- [Nàiseanta 4](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z8hhvcw)\n- [Nàiseanta 5](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zdpp34j)\n- [Àrd Ìre](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zqq4wxs)\n\n**Wales**\n\n- [Foundation Phase](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zxybmsg)\n- [KS2](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zbr9wmn)\n- [KS3](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z4kw2hv)\n- [GCSE](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z98jmp3)\n- [WBQ](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z9wtgdm)\n- [Essential Skills](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zhh7nrd)\n- [Cyfnod Sylfaen](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z4js6v4)\n- [CA2](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zbpwt39)\n- [CA3](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zh6vr82)\n- [CBC](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zqxy8mn)\n- [TGAU](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z8w76sg)\n\n**International**\n\n- [KS3](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zygcmbk)\n- [IGCSE](https:\/\/www.bbc.co.uk\/bitesize\/levels\/zgdqywx)\n\n**More from Bitesize**\n\n- [About us](https:\/\/www.bbc.co.uk\/bitesize\/articles\/z6x992p)\n- [All subjects](https:\/\/www.bbc.co.uk\/bitesize\/subjects)\n- [All levels](https:\/\/www.bbc.co.uk\/bitesize\/levels)\n- [Primary games](https:\/\/www.bbc.co.uk\/bitesize\/primary-games)\n- [Secondary games](https:\/\/www.bbc.co.uk\/bitesize\/secondary-games)\n\n- [National 5](https:\/\/www.bbc.co.uk\/bitesize\/levels\/z6gw2hv)\n# Practical electrical and electronic circuitsCalculating the value of the series resistor\nMeasurement and analysis of current and voltage in simple circuits allows us to formulate rules and predict unknown values.\n\nPart of [Physics](https:\/\/www.bbc.co.uk\/bitesize\/subjects\/z6fsgk7)[Electricity](https:\/\/www.bbc.co.uk\/bitesize\/topics\/zs2m97h)\n\nSave to My Bitesize\n\nSave to My Bitesize\n\nSaving\n\nSaved\n\nRemoving\n\nRemove from My Bitesize\n\nclose panel\n\n## In this guide\n1. [Revise](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/1)\n2. [Video](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/video)\n3. [Test](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/test)\n\n## Pages\n1. [Practical electrical and electronic circuits](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/1)\n2. [Voltage across components in a series circuit](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/2)\n3. [Parallel circuits](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/3)\n4. [Voltage across components in a parallel circuit](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/4)\n5. [Measuring resistance](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/5)\n6. [Electrical and electronic components](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/6)\n7. [Input devices](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/7)\n8. [Voltage dividers](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/8)\n9. [Output devices](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/9)\n10. [Calculating the value of the series resistor](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/10)\n11. [Process devices](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/11)\n\n## Calculating the value of the series resistor\nTo calculate the resistance of the series resistor required, we need to look at the current and voltage values recommended by the LED manufacturer.\n\nSuppose a manufacturer recommends a maximum voltage of \\\\(2V\\\\) across their LEDs and maximum current of \\\\(10mA\\\\).\n\nTo use one of these LEDs in a circuit powered by a \\\\(6V\\\\) battery close batteryA chemical supply of electrical energy. For example, common battery voltages include 1.5 V and 9 V., we would calculate the required series resistance as follows.\n\n![Circuit with a 6 V battery, resistor R and an LED connected in series.](https:\/\/bam.files.bbci.co.uk\/bam\/live\/content\/z99r87h\/small)\n\nUsing properties of a series circuit, the sum of the voltages across the LED and resistor R must equal the supply voltage.\n\n\\\\({V\\_s} = {V\\_{LED}} + {V\\_R}\\\\)\n\nNow substitute the supply voltage (\\\\(6V\\\\))and the maximum LED voltage (\\\\(2V\\\\)).\n\n\\\\(6 = 2 + {V\\_R}\\\\)\n\n\\\\({V\\_R} = 4V\\\\)\n\nSo the voltage across the series resistor will be \\\\(4V\\\\).\n\nIn a series circuit, the current is the same at all points.\n\nSo if the current in the LED is \\\\(10 mA\\\\), the current in resistor \\\\(R\\\\) is also \\\\(10 mA\\\\).\n\nUsing Ohm close OhmsThe unit of electrical resistance, whose symbol is Ω.'s Law, calculate the value of resistor required.\n\n\\\\(V = IR\\\\)\n\nRemember: \\\\(I\\\\)must be changed from \\\\(mA\\\\) to \\\\(A\\\\)(\\\\(10 mA = 0.01 A\\\\))\n\n\\\\(4 = 0.01 \\\\times R\\\\)\n\n\\\\(R = \\\\frac{4}{{0.01}}\\\\)\n\n\\\\(R = 400\\\\Omega\\\\)\n\nA \\\\(400 Ω\\\\) resistor is required.\n\n## Question\nA LED takes a current of \\\\(12.5 mA\\\\) when the voltage across it is 2 V.\n\nDraw a suitable circuit and calculate the value of the series resistor needed to operate the LED from a \\\\(9 V\\\\) battery.\n\n### Show answerHide answer\nThe circuit needed is:\n\n![Circuit with a 9 V battery, resistor R and an LED connected in series. The LED is labelled 2 V.](https:\/\/bam.files.bbci.co.uk\/bam\/live\/content\/zkkcd2p\/small)\n\nCheck that your LED symbol points towards the negative terminal (the shorter line) of the battery symbol.\n\nTo calculate the value of the series resistor, use the following steps:\n\nThe voltage of the supply splits up across components in series, so the voltage across the resistor is \\\\((9 - 2) = 7 V\\\\)\n\nThe current is the same through components in series, so the current in the resistor is 12.5 \\\\(mA (0.0125 A)\\\\).\n\nUsing the relationship between voltage, current and resistance gives:\n\n\\\\(R = \\\\frac{V}{I}\\\\)\n\n\\\\(= \\\\frac{7}{{0.0125}}\\\\)\n\n\\\\(= 560\\\\Omega\\\\)\n\nA \\\\(560 Ω\\\\) resistor is required.\n\n[Next pageProcess devices](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/11)\n\n[Previous pageOutput devices](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zk37hyc\/revision\/9)\n\n## More guides on this topic\n- [Electrical charge carriers](https:\/\/www.bbc.co.uk\/bitesize\/guides\/ztf74qt\/revision\/1)\n- [Potential differences (voltage)](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zsrpfg8\/revision\/1)\n- [Ohm's Law](https:\/\/www.bbc.co.uk\/bitesize\/guides\/z8b2pv4\/revision\/1)\n- [Electrical power](https:\/\/www.bbc.co.uk\/bitesize\/guides\/zsgtw6f\/revision\/1)\n- [Conductors and insulators](https:\/\/www.bbc.co.uk\/bitesize\/topics\/zs2m97h\/watch\/z3gg9j6)\n\n## Related links\n- [BBC Science](http:\/\/www.bbc.co.uk\/science\/0\/)\n- [BBC News: Science](http:\/\/www.bbc.co.uk\/news\/science_and_environment\/)\n- [BBC Lab UK](http:\/\/www.bbc.co.uk\/labuk\/)\n- [SQA National 5 Physics](http:\/\/www.sqa.org.uk\/sqa\/45731.html)\n- [Physics.org](http:\/\/www.physics.org\/)\n- [The Physics Classroom](http:\/\/www.physicsclassroom.com\/)\n- [Physics Central](http:\/\/www.physicscentral.com\/)\n\nLanguage:\n\n- [Home](https:\/\/www.bbc.com\/)\n- [News](https:\/\/www.bbc.com\/news)\n- [Sport](https:\/\/www.bbc.com\/sport)\n- [Earth](https:\/\/www.bbc.com\/future\/earth)\n- [Reel](https:\/\/www.bbc.com\/reel)\n- [Worklife](https:\/\/www.bbc.com\/worklife)\n- [Travel](https:\/\/www.bbc.com\/travel)\n- [Culture](https:\/\/www.bbc.com\/culture)\n- [Future](https:\/\/www.bbc.com\/future)\n- [Music](https:\/\/www.bbc.com\/culture\/music)\n- [TV](https:\/\/www.bbc.co.uk\/schedules\/p00fzl9m)\n- [Weather](https:\/\/www.bbc.com\/weather)\n- [Sounds](https:\/\/www.bbc.co.uk\/sounds)\n\n- [Terms of Use](https:\/\/www.bbc.co.uk\/usingthebbc\/terms)\n- [About the BBC](https:\/\/www.bbc.co.uk\/aboutthebbc)\n- [Privacy Policy](https:\/\/www.bbc.com\/usingthebbc\/privacy)\n- [Cookies](https:\/\/www.bbc.com\/usingthebbc\/cookies)\n- [Accessibility Help](https:\/\/www.bbc.co.uk\/accessibility)\n- [Parental Guidance](https:\/\/www.bbc.co.uk\/iplayer\/guidance)\n- [Contact the BBC](https:\/\/www.bbc.co.uk\/contact)\n- [BBC emails for you](https:\/\/www.bbc.co.uk\/bbcnewsletter)\n- [Advertise with us](https:\/\/www.bbc.com\/advertisingcontact\/)\n\nCopyright © 2025 BBC. The BBC is not responsible for the content of external sites. [Read about our approach to external linking.](https:\/\/www.bbc.co.uk\/editorialguidelines\/guidance\/feeds-and-links)","attrs_readable_markdown":null,"meta_canonical":null}

3. Robots.txt Check

Query:

Response:

4. Spam/Ban Check

Query:

Response:

5. Seen Status Check

ℹ️ Skipped - page is already crawled

📄

INDEXABLE

✅

CRAWLED

5 months ago

🚫

ROBOTS BLOCKED

Page Info Filters

Filter	Status	Condition	Details
HTTP status	PASS	`download_http_code = 200`	HTTP 200
Age cutoff	PASS	`download_stamp > now() - 6 MONTH`	5.8 months ago
History drop	PASS	`isNull(history_drop_reason)`	No drop reason
Spam/ban	PASS	`fh_dont_index != 1 AND ml_spam_score = 0`	ml_spam_score=0
Canonical	PASS	`meta_canonical IS NULL OR = '' OR = src_unparsed`	Not set

Page Details

Property	Value
URL	https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10
Last Crawled	2025-10-17 00:37:00 (5 months ago)
First Indexed	not set
HTTP Status Code	200
Meta Title	Calculating the value of the series resistor - Practical electrical and electronic circuits - National 5 Physics Revision - BBC Bitesize
Meta Description	In National 5 Physics examine the current and voltage in series and parallel circuits to formulate rules and determine unknown values.
Meta Canonical	null
Boilerpipe Text	To use one of these LEDs in a circuit powered by a \(6V\) battery close battery A chemical supply of electrical energy. For example, common battery voltages include 1.5 V and 9 V. , we would calculate the required series resistance as follows.
Markdown	[BBC Homepage](https://www.bbc.com/) - [Skip to content](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10#main-heading) - [Accessibility Help](https://www.bbc.co.uk/accessibility/) - [Your account](https://account.bbc.com/account?lang=en-GB&ptrt=https%3A%2F%2Fwww.bbc.co.uk%2Fbitesize%2Fguides%2Fzk37hyc%2Frevision%2F10) - [Home](https://www.bbc.com/) - [News](https://www.bbc.com/news) - [Sport](https://www.bbc.com/sport) - [Earth](https://www.bbc.com/future/earth) - [Reel](https://www.bbc.com/reel) - [Worklife](https://www.bbc.com/worklife) - [Travel](https://www.bbc.com/travel) - [Culture](https://www.bbc.com/culture) - [Future](https://www.bbc.com/future) - [Music](https://www.bbc.com/culture/music) - [TV](https://www.bbc.co.uk/schedules/p00fzl9m) - [Weather](https://www.bbc.com/weather) - [Sounds](https://www.bbc.co.uk/sounds) - [More menu](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10#global-navigation-more-menu) [More menu](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10#global-navigation-more-menu) [Search Bitesize](https://www.bbc.co.uk/bitesize/search?d=BITESIZE) - [Home](https://www.bbc.com/) - [News](https://www.bbc.com/news) - [Sport](https://www.bbc.com/sport) - [Earth](https://www.bbc.com/future/earth) - [Reel](https://www.bbc.com/reel) - [Worklife](https://www.bbc.com/worklife) - [Travel](https://www.bbc.com/travel) - [Culture](https://www.bbc.com/culture) - [Future](https://www.bbc.com/future) - [Music](https://www.bbc.com/culture/music) - [TV](https://www.bbc.co.uk/schedules/p00fzl9m) - [Weather](https://www.bbc.com/weather) - [Sounds](https://www.bbc.co.uk/sounds) [Close menu](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10#more-menu-button) [Bitesize](https://www.bbc.co.uk/bitesize) [Menu](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10#product-navigation-menu) - [Home](https://www.bbc.co.uk/bitesize) - [Learn](https://www.bbc.co.uk/bitesize/learn) - [Study support](https://www.bbc.co.uk/bitesize/study-support) - [Careers](https://www.bbc.co.uk/bitesize/careers) - [Teachers](https://www.bbc.co.uk/teach) - [Parents](https://www.bbc.co.uk/bitesize/parents) - [Trending](https://www.bbc.co.uk/bitesize/trending) - [My Bitesize](https://www.bbc.co.uk/bitesize/my) [More](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10#product-navigation-more-menu) England - [Early years](https://www.bbc.co.uk/bitesize/levels/zt6svwx) - [KS1](https://www.bbc.co.uk/bitesize/levels/z3g4d2p) - [KS2](https://www.bbc.co.uk/bitesize/levels/zbr9wmn) - [KS3](https://www.bbc.co.uk/bitesize/levels/z4kw2hv) - [GCSE](https://www.bbc.co.uk/bitesize/levels/z98jmp3) - [Functional Skills](https://www.bbc.co.uk/bitesize/levels/zvhtng8) Northern Ireland - [Foundation Stage](https://www.bbc.co.uk/bitesize/levels/znyh7nb) - [KS1](https://www.bbc.co.uk/bitesize/levels/zcwyp4j) - [KS2](https://www.bbc.co.uk/bitesize/levels/zjmj92p) - [KS3](https://www.bbc.co.uk/bitesize/levels/z3hbg7h) - [GCSE](https://www.bbc.co.uk/bitesize/levels/z98jmp3) Scotland - [Early Level](https://www.bbc.co.uk/bitesize/levels/zf7hgwx) - [1st Level](https://www.bbc.co.uk/bitesize/levels/zgckjxs) - [2nd Level](https://www.bbc.co.uk/bitesize/levels/zr48q6f) - [3rd Level](https://www.bbc.co.uk/bitesize/levels/zy4qn39) - [4th Level](https://www.bbc.co.uk/bitesize/levels/zvk2fg8) - [National 4](https://www.bbc.co.uk/bitesize/levels/zp3d7ty) - [National 5](https://www.bbc.co.uk/bitesize/levels/z6gw2hv) - [Higher](https://www.bbc.co.uk/bitesize/levels/zkdqxnb) - [Core Skills](https://www.bbc.co.uk/bitesize/levels/z66jhbk) - [An Tràth Ìre](https://www.bbc.co.uk/bitesize/levels/zggh6g8) - [A' Chiad Ìre](https://www.bbc.co.uk/bitesize/levels/zk3xy9q) - [An Dàrna Ìre](https://www.bbc.co.uk/bitesize/levels/z4y2scw) - [3mh ìre](https://www.bbc.co.uk/bitesize/levels/zmd346f) - [4mh ìre](https://www.bbc.co.uk/bitesize/levels/zxwb9ty) - [Nàiseanta 4](https://www.bbc.co.uk/bitesize/levels/z8hhvcw) - [Nàiseanta 5](https://www.bbc.co.uk/bitesize/levels/zdpp34j) - [Àrd Ìre](https://www.bbc.co.uk/bitesize/levels/zqq4wxs) Wales - [Foundation Phase](https://www.bbc.co.uk/bitesize/levels/zxybmsg) - [KS2](https://www.bbc.co.uk/bitesize/levels/zbr9wmn) - [KS3](https://www.bbc.co.uk/bitesize/levels/z4kw2hv) - [GCSE](https://www.bbc.co.uk/bitesize/levels/z98jmp3) - [WBQ](https://www.bbc.co.uk/bitesize/levels/z9wtgdm) - [Essential Skills](https://www.bbc.co.uk/bitesize/levels/zhh7nrd) - [Cyfnod Sylfaen](https://www.bbc.co.uk/bitesize/levels/z4js6v4) - [CA2](https://www.bbc.co.uk/bitesize/levels/zbpwt39) - [CA3](https://www.bbc.co.uk/bitesize/levels/zh6vr82) - [CBC](https://www.bbc.co.uk/bitesize/levels/zqxy8mn) - [TGAU](https://www.bbc.co.uk/bitesize/levels/z8w76sg) International - [KS3](https://www.bbc.co.uk/bitesize/levels/zygcmbk) - [IGCSE](https://www.bbc.co.uk/bitesize/levels/zgdqywx) More from Bitesize - [About us](https://www.bbc.co.uk/bitesize/articles/z6x992p) - [All subjects](https://www.bbc.co.uk/bitesize/subjects) - [All levels](https://www.bbc.co.uk/bitesize/levels) - [Primary games](https://www.bbc.co.uk/bitesize/primary-games) - [Secondary games](https://www.bbc.co.uk/bitesize/secondary-games) - [National 5](https://www.bbc.co.uk/bitesize/levels/z6gw2hv) # Practical electrical and electronic circuitsCalculating the value of the series resistor Measurement and analysis of current and voltage in simple circuits allows us to formulate rules and predict unknown values. Part of [Physics](https://www.bbc.co.uk/bitesize/subjects/z6fsgk7)[Electricity](https://www.bbc.co.uk/bitesize/topics/zs2m97h) Save to My Bitesize Save to My Bitesize Saving Saved Removing Remove from My Bitesize close panel ## In this guide 1. [Revise](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/1) 2. [Video](https://www.bbc.co.uk/bitesize/guides/zk37hyc/video) 3. [Test](https://www.bbc.co.uk/bitesize/guides/zk37hyc/test) ## Pages 1. [Practical electrical and electronic circuits](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/1) 2. [Voltage across components in a series circuit](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/2) 3. [Parallel circuits](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/3) 4. [Voltage across components in a parallel circuit](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/4) 5. [Measuring resistance](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/5) 6. [Electrical and electronic components](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/6) 7. [Input devices](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/7) 8. [Voltage dividers](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/8) 9. [Output devices](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/9) 10. [Calculating the value of the series resistor](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/10) 11. [Process devices](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/11) ## Calculating the value of the series resistor To calculate the resistance of the series resistor required, we need to look at the current and voltage values recommended by the LED manufacturer. Suppose a manufacturer recommends a maximum voltage of \\(2V\\) across their LEDs and maximum current of \\(10mA\\). To use one of these LEDs in a circuit powered by a \\(6V\\) battery close batteryA chemical supply of electrical energy. For example, common battery voltages include 1.5 V and 9 V., we would calculate the required series resistance as follows. ![Circuit with a 6 V battery, resistor R and an LED connected in series.](https://bam.files.bbci.co.uk/bam/live/content/z99r87h/small) Using properties of a series circuit, the sum of the voltages across the LED and resistor R must equal the supply voltage. \\({V\_s} = {V\_{LED}} + {V\_R}\\) Now substitute the supply voltage (\\(6V\\))and the maximum LED voltage (\\(2V\\)). \\(6 = 2 + {V\_R}\\) \\({V\_R} = 4V\\) So the voltage across the series resistor will be \\(4V\\). In a series circuit, the current is the same at all points. So if the current in the LED is \\(10 mA\\), the current in resistor \\(R\\) is also \\(10 mA\\). Using Ohm close OhmsThe unit of electrical resistance, whose symbol is Ω.'s Law, calculate the value of resistor required. \\(V = IR\\) Remember: \\(I\\)must be changed from \\(mA\\) to \\(A\\)(\\(10 mA = 0.01 A\\)) \\(4 = 0.01 \\times R\\) \\(R = \\frac{4}{{0.01}}\\) \\(R = 400\\Omega\\) A \\(400 Ω\\) resistor is required. ## Question A LED takes a current of \\(12.5 mA\\) when the voltage across it is 2 V. Draw a suitable circuit and calculate the value of the series resistor needed to operate the LED from a \\(9 V\\) battery. ### Show answerHide answer The circuit needed is: ![Circuit with a 9 V battery, resistor R and an LED connected in series. The LED is labelled 2 V.](https://bam.files.bbci.co.uk/bam/live/content/zkkcd2p/small) Check that your LED symbol points towards the negative terminal (the shorter line) of the battery symbol. To calculate the value of the series resistor, use the following steps: The voltage of the supply splits up across components in series, so the voltage across the resistor is \\((9 - 2) = 7 V\\) The current is the same through components in series, so the current in the resistor is 12.5 \\(mA (0.0125 A)\\). Using the relationship between voltage, current and resistance gives: \\(R = \\frac{V}{I}\\) \\(= \\frac{7}{{0.0125}}\\) \\(= 560\\Omega\\) A \\(560 Ω\\) resistor is required. [Next pageProcess devices](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/11) [Previous pageOutput devices](https://www.bbc.co.uk/bitesize/guides/zk37hyc/revision/9) ## More guides on this topic - [Electrical charge carriers](https://www.bbc.co.uk/bitesize/guides/ztf74qt/revision/1) - [Potential differences (voltage)](https://www.bbc.co.uk/bitesize/guides/zsrpfg8/revision/1) - [Ohm's Law](https://www.bbc.co.uk/bitesize/guides/z8b2pv4/revision/1) - [Electrical power](https://www.bbc.co.uk/bitesize/guides/zsgtw6f/revision/1) - [Conductors and insulators](https://www.bbc.co.uk/bitesize/topics/zs2m97h/watch/z3gg9j6) ## Related links - [BBC Science](http://www.bbc.co.uk/science/0/) - [BBC News: Science](http://www.bbc.co.uk/news/science_and_environment/) - [BBC Lab UK](http://www.bbc.co.uk/labuk/) - [SQA National 5 Physics](http://www.sqa.org.uk/sqa/45731.html) - [Physics.org](http://www.physics.org/) - [The Physics Classroom](http://www.physicsclassroom.com/) - [Physics Central](http://www.physicscentral.com/) Language: - [Home](https://www.bbc.com/) - [News](https://www.bbc.com/news) - [Sport](https://www.bbc.com/sport) - [Earth](https://www.bbc.com/future/earth) - [Reel](https://www.bbc.com/reel) - [Worklife](https://www.bbc.com/worklife) - [Travel](https://www.bbc.com/travel) - [Culture](https://www.bbc.com/culture) - [Future](https://www.bbc.com/future) - [Music](https://www.bbc.com/culture/music) - [TV](https://www.bbc.co.uk/schedules/p00fzl9m) - [Weather](https://www.bbc.com/weather) - [Sounds](https://www.bbc.co.uk/sounds) - [Terms of Use](https://www.bbc.co.uk/usingthebbc/terms) - [About the BBC](https://www.bbc.co.uk/aboutthebbc) - [Privacy Policy](https://www.bbc.com/usingthebbc/privacy) - [Cookies](https://www.bbc.com/usingthebbc/cookies) - [Accessibility Help](https://www.bbc.co.uk/accessibility) - [Parental Guidance](https://www.bbc.co.uk/iplayer/guidance) - [Contact the BBC](https://www.bbc.co.uk/contact) - [BBC emails for you](https://www.bbc.co.uk/bbcnewsletter) - [Advertise with us](https://www.bbc.com/advertisingcontact/) Copyright © 2025 BBC. The BBC is not responsible for the content of external sites. [Read about our approach to external linking.](https://www.bbc.co.uk/editorialguidelines/guidance/feeds-and-links)
Readable Markdown	null
Shard	132 (laksa)
Root Hash	2272746388958996332
Unparsed URL	uk,co,bbc!www,/bitesize/guides/zk37hyc/revision/10 s443