Mobile Phone Tool Kits

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How to Uninstall Apps from Downloaded Apps in Android 4.4.4 KitKat Device?

Command Line: Settings > Apps – DEVICE > Apps – DOWNLOADED.

1: Follow the Command Line to open up the ‘Apps, screen at your Android 4.4.4 KitKat device.

2: Tap any app which you want to uninstall. It will the open up the ‘App info’ screen of the app.  

3: Tap ‘Uninstall’ button. It will open up a prompt, asking you; ‘Do you want to uninstall this app?’  

4: Tap the ‘OK’ if you are sure that you want to uninstall the app.  

After few moments, the app will be uninstalled.

That’s all!

How to Automatically Back Up All Pictures on Your Android Phone to Google+

Follow the steps below to enable automatic backup of the photos on your Android Phone:

1. Power on your Android mobile phone.
   
2. Once the phone is unlocked, tap the Menu button to open the apps list.
   
   
3. Locate and tap the Photos icon to open the Photos Google+ app.
   Note: The Photos app is in-built in the Kitkat Android 4.4.
   
   
4. On the Photos app interface, tap the Menu button located on the upper-left corner of the screen.
   
   
5. From the drop-down list, tap Settings.
   
   
6. On the GENERAL SETTINGS interface, tap the Auto-Backup option.
   
   
7. Tap the switch located on the top-right corner of the screen to turn on the Sync or Auto-Backup feature of the Photos app to take automatic back up of the photos to the Google+ account.
   
   
8. Once done, close all the opened interfaces by tapping the back button multiple time In case your mobile phone does not have Android Kitkat, the below method can be followed to back up the photos to the Google+ account:
   
   
   1. Turn on your Android phone if it is turned off.
      
   2. Once the phone is unlocked, tap the Menu button to open the apps list.
      
   3. Locate and tap the Settings icon to open the Settings interface.
      
      
   4. Once the interface shows up, scroll down and tap Google under the Accounts section.
      
      
   5. In the opened interface, tap the Menu button located on the top-right corner.
      
      
   6. Tap Sync now to synchronize and backup your photos automatically to your Google+ account.
      
      
   7. Close all opened interfaces by tapping the back button several times.

Can't stop auto upload of pictures from Android to Drive

1. Open the Photos app .
2. Touch the menu button or icon  and select Settings.
3. Touch Auto Backup and switch the toggle On or Off.

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Smart phone repairing course

SWOT INSTITUTE                       

0772011040, 0711226562,0713924999, 0112691265

Advance Mobile Repairing Training – Syllabus

138,s.de.s.jayasinghe Rd, nugegoda

SWOT institute Nugegoda Next to BOC
First time in low price 5500/=
Recognized Certificated will be issued by us.
 Institute Awarded by Ministry of Education

1. Basic Mobile Phone Chip Level Training

•  History of Mobile Phone
•  GSM & CDMA Structure & Generation of Mobile Phone
•  Frequency & Channels
•  GPRS, Bluetooth, Infrared
•  Wi-Fi, SIM, & IMEI
•  Mobile Phone Assembly & Disassembly
•  Electronic Components Overview
•  Chip Level Soldering & De-soldering

2. Mobile Phone Complete Software Repairing

•  Parts of Computer
•  Computer Operating Driver Installation
•  Software Repairing
•  Mobile Phone S/W training with coding
•  Chinese Mobile Phone Repairing

3. Basic Electronics & Complete Mobile Hardware Repairing

•  Introduction to Electronics
•  Charge
•  Voltage
•  Types of current
•  Electronic Components Identification testing & working

4. Complete training for Hardware Repairing

•  Tips for Mobile repairing
•  Hardware Repairing
•  Section of Mobile Phones
•  Circuit Diagram Reading
•  GSM Mobile Phone Troubleshooting
•  Chinese Mobile phone Troubleshooting
•  CDMA Mobile phone Troubleshooting
•  Practically handset repairing
•  Tips for service centre

Want to join Laptop Repairing Course call @ 077 2011040

How To Fix A Wet Cell Phone

Learn how to fix, repair and save your wet cell phone if it gets water-logged. The next time when your get your cell phone gets soaked or drenched in water, tea or coffee, just remember and follow these simple and easy first aid measures. You will be more than happy and surprised to see your priceless gadget be it a smartphone, a tablet or ipod in working condition. You won’t get frustrated of running around repair centers if you follow these simple tips.


Most people don’t know the basic steps to avoid a wet cellular phone from getting damaged. The most important thing is to follow the procedure to avoid damages to the printed circuit board (PCB) of the cell phone. Preventing damage to the PCB (also called motherboard) should be the main aim as you lose warranty on the handset due to water-logging and in such cases most of the service centers don’t provide a new circuit board and it is also not available with spare part sellers.

Steps To Repair And Fix A Wet Cell-Phone:

1. Remove the battery immediately: This is important so that current does not flow freely in the motherboard and don’t just switch-off the handset. Just switching of the handset is not enough, you have to remove the battery.
2. Dismantle your cell phone: Open up your cell phone carefully. You can see videos of dismantling method for your particular model on youtube! You may need opening tools as well as screw driver for dis-assembly.
3. Dry the circuit board completely: The green coloured circuit board carefully and completely. You can use a hair drier or you can also dry it in direct sunlight. Just make sure you dry it completely!
4. Also dry all the spare parts and components: You also need to dry the components as well as the body so that nothing remains wet. Be careful that you do not break the LCD as it is very delicate.
5. Clean the circuit board: Clean the entire PCB with spirit or alcohol using a brush. This will prevent corrosion on the PCB.

When you finish with all the above steps, you can re-assemble your phone. Now check if your phone switches on. If yes, you are a lucky man! If no, don’t get dejected, you still have one more option. You can connect it to computer and see if it is getting detected. If yes, update it online and check again. If it does not switch on, charge your handset and try again. And if it is not getting detected in computer, dismantle your handset again and give mild heat (not more than mild!) all over the PCB and check again. If it doesn’t switch on now, you are not lucky enough! You will have to visit a repair center.

Some people also keep the water-damaged phone submerged in a bag of rice to absorb all the moisture. It is a good thing giving positive results, but still not enough if there is more water inside the handset.

Note: If you do not know how to go about the above procedures, don’t repair it yourself. You are more likely to damage the handset further. Just remove the battery immediately when it falls in get it fixed at repair centers.

Please also post your valuable suggestions on further prevention and protection in the comments section below.

Difference Between Soft Reset And Hard Reset In Cell Phones

Cell phones today perform a wide range of tasks which were not even thinkable 10 years ago. Hence there are always chances of malfunctioning even without a cause. Most of the smartphones today tend to start showing abnormalities after completing their honeymoon period!

The hardware related problems and faults like broken screen, no outgoing or incoming sound, no charging, SIM detection failure require the handset to opened and thereafter either serviced or parts to be replaced. But the software problems can be easily repaired by anyone either by soft-reset or hard-reset.

The most common software problems are as follows:    (SWOT INSTITUTE 0772011040)

• Freezing or becoming unresponsive
• Getting stuck on logo while booting
• Slow processing
• Blank screen without booting
• Switching off automatically
• Improper functioning of apps

To overcome the above faults, we first try soft-reset. If the problem is not solved, we then try hard-reset.

So lets know what is the difference between soft-reset and hard-reset.

Soft-Reset:
Rebooting or restarting your cell phone is called soft-reset. You just need to press the power button to switch it off. If it is not switching-off, keep the power button pressed for 15-20 seconds until it shuts down.
In basic, normal, feature phones, there is an option in the menu to reset settings only. This will reset only the settings and not delete the data. If this option is available, you can also try it as it solves many of the minor software-related faults. But this option is not available in smartphones; it is only available in cheap, low-end phones.

Hard-Reset:
Hard-rest (also known as factory-reset) means deleting all the user data in your handset. It will delete all data which you have downloaded or saved in your handset including contact numbers, music, pictures, videos, apps, etc. It also brings the handset back to its original settings. It will not delete the data in the memory card by this procedure.

Hard-reset will delete the following data

• Google account / Phone account
• Downloaded apps and their data.
• App settings
• Contacts, messages, music, pictures, videos, etc.

Things to check before performing a hard-reset

• Backup of necessary data is taken.
• Battery should be charged enough to last at least 10-15 minutes.

Caution: Before doing any procedure, we need to know the root cause of the fault. If the problem is not known, the procedure to be followed is by ‘trial and error’ i.e. try step by step. First try a soft-reset, and then try a hard-reset. If the fault is not yet resolved, you will need to flash or upgrade your mobile phone.

Did this article help you out? Please let us know by leaving a comment below!

How To Hard Reset Sony Xperia Z1 – All Methods

How To Hard Reset Sony Xperia Z1

Learn how to make a hard reset or format Sony Xperia Z1 by using any of our simple methods. Sony Xperia Z1 code named ”Honami” is a high-end Android smartphone produced by Sony. It is water as well as dust proof with a 20.7 megapixel camera and is shipped with Android 4.2 (Jelly Bean) operating system.
Hard-reset means to format i.e you delete all the data in the phone memory. Many mobile repairing technicians do not know how to open pattern locks. With a hard reset through key combinations, you can easily open pattern locks in Android phones.The cell phone will also come back to its original factory settings. It is also called master-reset and even alternate reset. We are showing here all the methods to hard-reset your Xperia Z1.
You should first try a soft-reset i.e to re-boot your handset. Just press the power button until it shuts down and then restart it. If the fault gets resolved, you do not need to perform a hard-reset.

When is hard-reset required?

• If you want to bring your phone back to its default settings.
• If your device is infected by any virus.
• If your handset is functioning very slowly.
• If it gets stuck, freezes, hangs or become unresponsive frequently.
• Some of the apps are crashing and not functioning properly and you are unable to even uninstall them manually.
• If there is some software or OS related problem which you cannot resolve by basic methods.
• When you are planning to sell your handset and want to delete all your personal data.
• If you have forgotten phone code or user code.
• When your handset is pattern locked due to too many wrong pattern attempts. You have forgotten the pattern as well as the gmail account ID or password associated with that device. ( if you know the gmail ID and password of that handset, you can recover the pattern and save your data.)

Read Difference between hard reset and soft reset in cell phones
Learn how to backup and restore an android cell phone

There are 3 methods of doing a hard reset on Sony Xperia Z1

1. Hard-Reset through physical button:

You can format Sony Xperia Z1 by a special physical button. Just remove the memory card and besides the SD card slot, you will find a small red coloured button. Press and hold this button for 3 to 10 seconds. The phone will now shut down. Now press the power button to switch it on.
2. Hard-Reset through settings:
This is the most simple and easy method and is possible if you are able to access the menu and go to settings.

1. Search for the settings option in the menu.
2. Now select ‘Backup Ad Restore’
3. Now select the ‘Factory Data Reset’ option.
4. Now select ‘Reset Phone’ option.
5. Now tap on ‘Erase Everything’. The process will take some time and the handset will now restart. It will then restart.

3. Hard-Reset through key combinations:
If you cannot access the menu due to pattern lock or booting related problems, you can use this option.

Volume Up + Power Button

1. Switch-off your handset
2. Press the power button volume up button simultaneously and hold until you see the android logo.
3. You will see an option – Wipe data/Factory reset. Go to this option with volume down button. Select this option with power button.
4 Now come down to the option – delete all user data with volume down option and select it with power button.
5. The device will now be formatted. After this select the option – reboot system now by pressing the power button.
Perform a factory data reset only if absolutely necessary as it will remove all the below things including all your data:

• Google account
• Downloaded apps and their data.
• App settings
• Contacts, messages, music, pictures, videos, etc.

If your problem or fault is still not resolved after performing a hard reset, you will have to flash or update your cell phone.
Note:
1. Hard reset erases all data, so take a backup of all your data if possible before performing a hard-reset to an external device.
2. It is important that your phone battery is charged enough to last the procedure i.e atleast for 10-15 minutes.
Please let us know if any of the above method is not working. Please also let us know if the above procedure solved your problem or not in the comments section below.

How To Check A Ringer (Loud Speaker) In Cell Phones

A ringer, also called a loud speaker is a speaker through which you hear ringtone and music. During a call, when you activate the loud speaker, the louder voice which you start hearing also comes from the ringer. It is also called a buzzer in basic low-end mobile phones. Its work is to convert electrical signal into sound.

If the ringer becomes faulty, you will not be able to below 3 sounds:

• Ringtone
• Music
• Loud speaker’s voice during a call

To avoid missing calls, you can switch on the vibration as a temporary solution! The method to check it will be the same for any brand or model of a mobile phone or a tablet be it an iPhone, a Samsung Galaxy, a Sony Xperia or a Nokia.

Steps to check ringer of a cell phone

1. Turn off your cell phone and dismantle it carefully. If you do not know how to dismantle your handset, you can watch videos of its disassembly procedure on Youtube!
2. Now remove the ringer carefully. It can be located anywhere inside the casing. The best way to locate it is – it will be below the opening (hole) in the casing from where you hear music! Do not misunderstand and remove the speaker by mistake. The speaker is meant to hear the calling person’s voice during a call and is a different spare part.
3. Now keep the multimeter on continuity setting. On this setting when you touch the tip of the red and black probes to each other, you will be able to hear a beep sound.
4. Now touch the tip of the 2 probes of the multimeter (the red and the black wires) to the 2 terminals (pins) of the ringer. Now if you hear a beep sound, then your ringer is good and working. And if you do not hear any beep sound, then your ringer is faulty.

Read How to use multimeter in cell phone repairs

Second method to check loud speaker

The other option to check or test a loud speaker of a mobile phone or a tablet is to put it in any other same working model (or a handset with the same size speaker) and check if its working properly in it. If its not working, its faulty. It’s as simple as that! In some models, the ringer comes as an entire unit. In such cases, you will have to replace the entire unit.

Note: If your ringer is ok and still you are unable to hear ringtone during a call and music as well, then check if it is connecting properly with the PCB. Clean its contact points on the PCB (Printed Circuit Board) with an eraser. If the ringer is soldered, you will have to check if its soldered properly. If its not, resolder it properly. Also try replacing with a new one. Still if the fault doesn’t go, there may be a complicated hardware problem in the PCB. It will either be due to a broken track supplying voltage to the ringer or a faulty IC. You will have to repair it by following schematic diagrams. Always check the ringer settings whether its not kept on mute before opening your handset.

cell phone mic checking

SWOT INSTITUTE 077 2011040

In cell phones, during a call, when you speak, your voice goes into the mic. A mic converts voice into electrical signal. It is also called microphone and mouthpiece. It will always be at the buttom, inside a cell phone. If it becomes faulty, your voice will not be heard by the person you are talking to. You can try using an earphone (headset) and try if your voice is being transmitted! The method to check it will be the same for any brand or model of a mobile phone or a tablet be it an iPhone, a Samsung Galaxy, a Sony Xperia or a Nokia. You can check it with either a digital or an analog multimeter, but most technicains today prefer digital multimeters as analog ones are outdated.

Steps to check mic of a cell phone

1. Turn off your cell phone and dismantle it carefully. If you do not know how to dismantle your handset, you can watch videos of its disassembly procedure on Youtube!
2. Now remove the mic which is located at the buttom. There is a small hole at the buttom of the casing (body panel) for the voice to enter the mic. The mic will always be exactly below it inside the casing.
3. Now keep the multimeter on resistance setting. It may be indicated by the symbol ‘Ώ’. In resistance too, there are many settings. Keep it on 20K or 20KΏ setting.
4. Now touch the tip of the 2 probes of the multimeter (the red and the black wires) to the 2 terminals (pins) of the mic. Now move your mouth very near to the mic and blow air into its hole. If the reading on the screen increases rapidly, your mic is good and working. In most mics, the reading rapidly increases to around 100. And if the reading is still 1 after blowing air, your microphone is faulty.

Read our guide How to use multimeter in cell phone repairs

Second method to check microphone

The other option to check or test mic of a mobile phone or a tablet is to put it in any other same working model (or a handset with the same shape and size mic) and check if its working properly in it. If its not working, its faulty. It’s as simple as that! For checking, its not necessary to call someone. You can check it through voice recorder function easily.

Note: If your mic is ok and still your voice is not being transmitted during a call, check if it is connecting properly with the PCB. Clean its contact points on the PCB (Printed Circuit Board) with an eraser. If the mic is soldered, you will have to check if its soldered properly. If its not, resolder it properly. Also try replacing with a new one. Still if the fault doesn’t go, there may be a complicated hardware problem in the PCB. It will either be due to a broken track which is supplying voltage to the mic or due to a faulty IC. You will have to repair it by following schematic diagrams.

How To Check A Speaker In Cell Phones

SWOT INSTITUTE 077 2011040

In cell phones, you hear the voice of the calling person in your ears through the speaker. The speaker converts electrical signal into voice. It is also called an earpiece. It will always be on the top, inside a cell phone. If it becomes faulty, you will not be able to hear the voice of the calling person during a call. In such cases you can turn on the loud speaker as a temporary relief! The method to check it is the same for any brand or model be it an iPhone, a Samsung Galaxy, a Sony Xperia or a Nokia. You can check it with either a digital or an analog multimeter, but most technicains today use digital multimeters as analog ones are outdated.


Steps to check speaker of a cell phone

1. Switch off the cell phone and dismantle it carefully. If you do not know how to dismantle your cell phone or tablet, you can watch videos of its dis-assembly procedure on Youtube!
2. Now remove the speaker which is located on the top. It will be below the top opening on the panel from where the voice during a call comes out. Do not remove the loud speaker (ringer)by mistake.  The ringer is a different part and it looks almost the same like a speaker. But it is the part through which you hear ringtone and music. In some low end models, the speaker as a ringer also and hence in such models, there wont be a separate ringer.
3. Now keep the multimeter on continuity setting and touch the tip of the 2 probes (one is red and the other black) on any 2 terminals of the speaker.
4. If you hear a beep sound, the speaker is OK. In some multimeters and speakers, instead of beep sound, you will see a reading between 25 to 45. The speaker is good and working even if you get a reading between this range. And if you do not hear beep sound and there is no reading then your speaker is faulty.

Second method to check speaker

The other option to test or check the speaker of a mobile phone or a tablet is to put it in any other same working model (or a handset with the same size speaker) and check if its working in it. If its not working, its faulty. It’s as simple as that!

Note: If your speaker is ok and still you are not able to hear the calling persons sound, check if it connecting properly with the PCB. Clean its contact points on the PCB (Printed Circuit Board) with an eraser. If the speaker is a soldered one, you will have to check if its soldered properly. If its not, resolder it properly. Also try replacing with a new one. In some models, the speakers come as an assembly unit. In such models, you will have to replace the entire unit. Still if the fault doesn’t go, there may be a complicated hardware problem in the PCB. It will either be due to a broken track supplying voltage to the speaker or due to a faulty IC. You will have to repair it by following schematic diagrams.

How To Check Shorting In Mobile Phones

SWOT INSTITUTE  077 2011040

The first thing you have to check in dead mobile phones after checking the battery is shorting. And if it is short, you will first have to remove it to get it repaired. All technicians should know how to remove a short circuit in cell phones.

Reasons for shorting in mobile phones:

1. Phone falling in water. This is the most common reason
2. Handset overheating.
3. Using an incompatible or faulty charger for charging
4. Sometimes, sparks or smoke coming out of the handset due to any reason.

We have to understand the below 2 terms of electronics to understand shorting better:

1. Open circuit: If a track is broken, then it is said that the track is open.
2. Short circuit: If 2 parallel separate tracks touch each other due to some fault, it is called short circuit.

Note: In circuit boards of cell phones, tablets or any other electronic device, there are tracks instead of wires through which current flows. Hence we use the term ‘tracks’ instead of wires or cables.

Option 1.

How to check shorting in mobile phones with multimeter:

We can easily check whether there is shorting in the circuit board or not with the help of a multimeter. Follow the steps below:

1. Keep the multimeter on continuity setting (Also called diode setting)

2. Identify the positive and negative terminals of the battery connector. The positive terminal (+) is the pin of the battery connector where the positive terminal of the battery touches on it. It is also called vBat (Battery Voltage) pin. While negative terminal (-) is the pin of the battery connector where the negative terminal of the battery touches on it. It is also called GND (Ground) pin.

3. Now touch the red probe (+) of the multimeter to negative terminal of the battery connector.

If you see any reading on the multimeter or hear a continuous beep sound, then the motherboard is short i.e your mobile phone is short. And if there is no reading or no continuous beep sound, the board is not short. If you are using an analogue multimeter, keep it on Ohms(x10) setting. If the pointer (needle) moves even a little, than it is short, otherwise, it’s okay.

Option 2.

How to check shorting in mobile phones with DC Power Supply:

A DC Supply is also called jhatka machine or battery eliminator. Its work is to convert AC voltage coming from an AC volt source to DC voltage. To check shorting, follow the step below:

1. Switch on the DC power supply. Now select the output voltage as much as its battery voltage. You can read it on the battery. In most phones, it is 3.7v or 3.8v. Some Chinese phones have output of 4.2 volt.

2. Connect red probe to the positive terminal of the battery connector (vBat pin) and the black probe to the negative terminal (GND)as well as the 3rd pin called BSI. And do not touch any other key or button.

Now, if you see any amount of current on the screen, then it means, the circuit board is short.

And if, there is the screen shows ‘0.00’ in the current reading, then it is okay.

Problems in handset if it is short:

• Dead
• Battery drains and discharges fast
• Overheating
• Hanging
• Switches off automatically or restarts.

How To Use A Multimeter In Mobile Phone Repairs

SWOT INSTITUTE  077 2011040
Learn how to use a multimeter in mobile phone repairs by reading this guide. A multimeter is used for testing and to check readings of various parts and components in a mobile phone.


SWOT INSTITUTE 077 2011040

There are two types of multimeters available in the market. They are

1. Digital Multimeter
2. Analog Multimeter

You can use any type of the ones mentioned above as both of them will do the same thing. The only difference is that a digital one will show you the readings in digital format thereby saving you time and effort. While in an analog one, you will have to see the reading as per the arrow on its screen. Most technicians prefer to use the digital models. The analog models are used by old generation technicians, as they love and have a distinct affinity to them!

A multimeter whether digital or analog has two wires (also called probes), a red and a black wire. The red probe is positive (+), while the black probe is negative(-). In electronics, always red is positive and black is negative.

When you buy a new multimeter, insert one end of the red probe in VΩ slot (round hole), and the black probe in the COM (means common) slot. The 3^rd slot i.e 10A or 20A is not used in cell phone repairs.

In mobile phone repairs, we use only any 1 of the below given settings in multimeter:

1. DC Volt Setting: We use this setting to check the voltages of the things to be checked. In DC volt setting the output voltage of various things like battery, battery connector, charger, charging connector, etc. can be checked. It is indicated by a capital V and straight line with 3 dots below it.

Read how to check voltage of a cell phone battery

2.  Resistance Setting:  By this meter, the resistance of various parts like resistors, etc can be checked. We can also check resistance between 2 points if it is instructed to check in a service manual to check it to get a particular reading while repairing a fault in the motherboard. We can also check the microphone of cell phone with this setting.

Read how to check a resistor in cell phones.

3.  Continuity:  This is also called diode setting. When you touch the red and the black probe ends while on this setting, you will be able to hear a beep sound. By keeping the multimeter on this setting, we can check the continuity between the given 2 points. We can check whether the tracks are open or not. If the multimeter shows continuity, it will give a beep sound. That will mean that the track is ok. And if it does not beep, it will mean that the track is broken. To repair a broken track, all technicians make jumpers. Jumpering means soldering a thin insulated wire from one end of a broken track to the other end.

With this setting, we also check whether the circuit board is short or not. We check the shorting by keeping the wires on the positive and negative terminals of the battery connector and also reverse the wires. If we get beep sound both ways then the circuit board is short, if we get beep sound only once then it is not short.

In some models of cell phones, you will not hear the beep sound. Instead you will either see some reading (like 255, 282, etc) on the screen of the multimeter or just 1. So if you see reading 2 times i.e even after reversing the probes, then the circuit board is short. You should get reading one time and just 1 on the other time.

Free Cellphone Repair Tutorial Sitemap

SWOT INSTITUTE 077 2011040

This is where you can learn a step by step from basic to advance procedure on how to fix major mobile phone handsets problems such as Nokia, iPhone, Blackberry, Samsung, SonyEricsson, Motorola, HTC, Android,LG, Siemens, Benq and etc. for absolutely 100% Fre

All lessons herein were all simplified and a few general technical terms being reduced to make easy learning and understanding, Images and Pictures were also gathered and choose appropriately to support every aspects of   learning.

LESSON 01

Basic Information How Cellphone Works?
Learning with Block Diagram on How basically Cell-phone works?

 

 SWOT INSTITUTE 077 2011040

Ohm's Law

• Calculate

What is Ohm's Law?

Ohm's Law is made from 3 mathematical equations that shows the relationship between electric voltage, current and resistance.

What is voltage? An anology would be a huge water tank filled with thousands of gallons of water high on a hill.
The difference between the pressure of water in the tank and the water that comes out of a pipe connected at the bottom leading to a faucet is determined by the size of the pipe and the size of the outlet of the faucet. This difference of pressure between the two can be thought of as potential Voltage.

What is current? An analogy would be the amount of flow determined by the pressure (voltage) of the water thru the pipes leading to a faucet. The term current refers to the quantity, volume or intensity of electrical flow, as opposed to voltage, which refers to the force or "pressure" causing the current flow.

What is resistance? An analogy would be the size of the water pipes and the size of the faucet. The larger the pipe and the faucet (less resistance), the more water that comes out! The smaller the pipe and faucet, (more resistance), the less water that comes out! This can be thought of as resistance to the flow of the water current.
All three of these: voltage, current and resistance directly interact in Ohm's law.
Change any two of them and you effect the third.

Info: Ohm's Law was named after Bavarian mathematician and physicist Georg Ohm.

Ohm's Law can be stated as mathematical equations, all derived from the
same principle.
In the following equations,
V is voltage measured in volts (the size of the water tank),

I is current measured in amperes (related to the pressure (Voltage) of water thru the pipes and faucet) and

R is resistance measured in ohms as related to the size of the pipes and faucet:

V = I x R (Voltage = Current multiplied by Resistance)

R = V / I (Resistance = Voltage divided by Current)

I = V / R (Current = Voltage Divided by Resistance)

Knowing any two of the values of a circuit, one can determine (calculate) the third, using Ohm's Law.

For example, to find the Voltage in a circuit:

If the circuit has a current of 2 amperes, and a resistance of 1 ohm, (< these are the two "knowns"), then according to Ohms Law and the formulas above, voltage equals current multiplied by resistance:

(V = 2 amperes x 1 ohm = 2 volts).

To find the current in the same circuit above assuming we did not know it but we know the voltage and resistance:
I = 2 volts divided by the resistance 1 ohm = 2 amperes.

In this third example we know the current (2 amperes) and the voltage (2 volts)....what is the resistance?
Substituting the formula:
R = Volts divided by the current (2 volts divided by 2 amperes = 1 ohm

Sometimes it's very helpful to associate these formulas Visually. The Ohms Law "wheels" and graphics below can be a very useful tool to jog your memory and help you to understand their relationship.





The wheel above is divided into three sections:

Volts V (on top of the dividing line)
Amps (amperes) I (lower left below the dividing line)
Resistance R (lower right below the dividing line)
X represents the (multiply by sign)
Memorize this wheel

To use, just cover the unknown quantity you need with your minds eye and what is left is the formula to find the unknown.

Example:

To find the current of a circuit (I), just cover the I or Amps section in your mines eye and what remains is the V volts above the dividing line and the R ohms (resistance) below it. Now substitute the known values. Just divided the known volts by the known resistance.
Your answer will be the current in the circuit.
The same procedure is used to find the volts or resistance of a circuit!

Here is another example:

You know the current and the resistance in a circuit but you want to find out the voltage.

Just cover the voltage section with your minds eye...what's left is the I X R sections. Just multiply the I value times the R value to get your answer! Practice with the wheel and you'll be surprised at how well it works to help you remember the formulas without trying!
This Ohm's Law Triangle graphic is also helpful to learn the formulas.
Just cover the unknown value and follow the graphic as in the yellow wheel examples above.

You'll have to insert the X between the I and R in the graphic and imagine the horizontal divide line but the principal is just the same.






In the above Ohm's law wheel you'll notice that is has an added section (P) for Power and the letter E* has been used instead of the letter V for voltage.
This wheel is used in the exact same fashion as the other wheels and graphics above.
You will also notice in the blue/green areas there are only two known values with the unknown value in the yellow sections. The red bars separate the four units of interest.

An example of the use of this wheel is:
Let's say that you know the power and the current in a circuit and want to know the voltage.
Find your unknown value in the yellow areas (V or E* in this wheel) and just look outward and pick the values that you do know. These would be the P and the I. Substitute your values in the formula, (P divided by I) do the math and you have your answer!

Info: Typically, Ohm's Law is only applied to DC circuits and not AC circuits.
* The letter "E" is sometimes used in representations of Ohm's Law for voltage instead of the "V" as in the wheel above.

 

 

 

 

 

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