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Calculate terminal voltage instantly using our free Terminal Voltage Calculator. Easy, accurate, and perfect for students and engineers.
Vt = EMF - (I × R)
Ever wondered why a battery’s voltage sometimes reads lower when it’s connected to a circuit? That’s because of something called terminal voltage. It’s the actual voltage you get across the battery terminals when current is flowing.
We’ve built this Terminal Voltage Calculator to make things super easy. You’ll just enter the EMF, current, and resistance and boom, you’ll see your result in seconds. No tricky math, no stress.
Terminal voltage is the real voltage available at a battery’s terminals when it’s supplying current. It’s usually a bit lower than the battery’s EMF due to internal resistance.
For instance, if your car battery reads 12.6 volts when idle but drops to 11.8 volts when you start the engine, that drop happens because of the internal resistance and the current flow.
The formula to calculate terminal voltage is simple:
Vt = EMF − I × R
Where:
This equation shows that as current increases, the voltage drop across internal resistance also increases, which lowers the terminal voltage.
Let’s go through an easy example.
Example 1:
A battery has an EMF of 100 volts, carries a current of 5 amps, and has an internal resistance of 3 ohms.
Using the formula:
Vt = 100 − (5 × 3)
Vt = 100 − 15
Vt = 85 volts
So, the terminal voltage is 85 volts.
Example 2:
EMF = 150 volts, Current = 2 amps, Resistance = 20 ohms
Vt = 150 − (2 × 20)
Vt = 150 − 40
Vt = 110 volts
Here, the terminal voltage is 110 volts.
You don’t need to be a physics pro to use this tool. Here’s how it works:
Our tool instantly shows the terminal voltage, along with each calculation step. You’ll see how the EMF, current, and resistance affect the final result.
The Terminal Voltage Calculator is a must-have tool for anyone studying or working with circuits. It shows you exactly how current and resistance affect the usable voltage from a power source.
Just enter your values and let the calculator do the heavy lifting. Simple, accurate, and designed to help you learn as you calculate.
EMF is the total potential difference the source can provide. Terminal voltage is the voltage you get when current actually flows it’s EMF minus the internal loss.
Because of the voltage drop across internal resistance. When current flows, some energy is lost inside the source.
Yes, in charging conditions. When current flows into the battery, the terminal voltage can rise above EMF.
It’s measured in volts (V).
If resistance is zero, terminal voltage equals EMF meaning no energy loss.