# Calculating Terminal Voltage: Battery with 3.0V EMF and 0.70 Ohm Resistance

• sp1974
In summary, the conversation involved a homework problem concerning terminal voltage and the use of Ohm's law. The initial question was about finding the terminal voltage of a battery with given emf and internal resistance. The conversation then discussed the use of current instead of ampere and how Ohm's law can be used to calculate the current in the circuit. Finally, the solution was found by finding the current and using it to calculate the voltage drop across the internal resistor.

#### sp1974

I have another homework problem involving termal voltage that I am stuck on since an Ampere wasn't given any help?

A battery whose emf is 3.0 V. and whose internal resistance is 0.70 ohms is connected to a circuit whose net resistance is 14.7 ohms. What is the terminal voltage of the battery?

It's true, the current was not given to you, because you can calculate the current in this circuit using Ohm's law. That is the whole point of the question.

cepheid said:
It's true, the current was not given to you, because you can calculate the current in this circuit using Ohm's law. That is the whole point of the question.

Yeah but don't you use intermal resistance * ampere to figure a number for voltage and than take that and subtract from emf to figure terminal voltage?

sp1974 said:
Yeah but don't you use intermal resistance * ampere to figure a number for voltage and than take that and subtract from emf to figure terminal voltage?

First of all, it's not "ampere." The name of the physical quantity you are measuring is 'current.' An 'ampere' is the name of the unit by which current is measured. What you are saying is an equivalent mistake to saying that force = "kilogram" * acceleration. Try not to confuse the names of quantities in physics with the names of the units used to measure those quantities.

Secondly, it is true that the voltage across the internal resistor will be the current through it multiplied by its resistance. The point I was trying to make was that it's okay that you haven't been given this current, because you can use Ohm's law for the whole circuit in order to calculate what the current is. (Hint: you have two resistors in series).

So 3.0V = I(R1 + R2)

3V = I (15.4) and than solve for I which would be .1948A?

sp1974 said:
So 3.0V = I(R1 + R2)

3V = I (15.4) and than solve for I which would be .1948A?

Yeah, that's right.

But the question is asking for terminal voltage of the battery and this is in Ampere not volts.

sp1974 said:
But the question is asking for terminal voltage of the battery and this is in Ampere not volts.

Yeah, but now that you have the current, you can do what you yourself suggested in post #3 in order to find the voltage across the internal resistor. It was a two-step problem. Do you understand? You needed to find the current through the circuit in order to find the voltage drop across the internal resistor.

sweet! 2.86V thanks!

## 1. What is thermal voltage?

Thermal voltage is the voltage generated by the temperature difference between two points in a material, according to the Seebeck effect. It is also known as thermoelectric voltage or Seebeck voltage.

## 2. How is thermal voltage calculated?

Thermal voltage can be calculated using the Seebeck coefficient, which is a measure of the material's thermoelectric properties, and the temperature difference between the two points.

## 3. What is the relationship between thermal voltage and temperature?

The thermal voltage of a material is directly proportional to the temperature difference between the two points. As the temperature difference increases, so does the thermal voltage.

## 4. Why is thermal voltage important in scientific research?

Thermal voltage is important in scientific research because it allows us to measure temperature differences and understand the thermoelectric properties of different materials. It is also used in various applications, such as thermocouples and thermoelectric power generators.

## 5. How does thermal voltage differ from electrical voltage?

Thermal voltage is generated by temperature differences, while electrical voltage is generated by the movement of electrons. They have different units of measurement and are used for different purposes in scientific research and technology.