Why EMF of cell is always greater than its terminal voltage

Last Updated on 12 months by Francis

In this topic, we will explore why the electromotive force (EMF) of a cell is always greater than its terminal voltage. The EMF of a cell is the maximum potential difference that can be generated between the electrodes of a cell when no current is flowing. On the other hand, the terminal voltage is the actual potential difference across the electrodes when a current is flowing through the cell. While the EMF and terminal voltage may seem interchangeable, there are several factors that contribute to the difference in values. Let’s delve into these factors further to understand why the EMF of a cell is always greater than its terminal voltage.

Understanding EMF and terminal voltage

Electromotive force (EMF) and terminal voltage are two important concepts in the world of electrical engineering. EMF is the amount of electrical energy that a battery or cell can supply, while terminal voltage is the amount of energy that is actually available to be used by a device. The EMF of a cell represents the maximum possible voltage that can be delivered by the cell, while the terminal voltage is the actual voltage that is delivered to a device when it is connected to the cell. In this essay, we will explore why the EMF of a cell is always greater than its terminal voltage.

Factors that affect terminal voltage

Several factors affect the terminal voltage of a cell, including the internal resistance of the cell, the load resistance, and the amount of current flowing through the circuit. When a device is connected to a cell, the internal resistance of the cell causes a voltage drop, reducing the terminal voltage. The load resistance also affects the terminal voltage, as a higher load resistance will cause a greater voltage drop across the cell’s internal resistance, reducing the terminal voltage. Finally, the amount of current flowing through the circuit also affects the terminal voltage, as a higher current will cause a greater voltage drop across the cell’s internal resistance.

Factors that affect EMF

The EMF of a cell is affected by several factors, including the type of cell, the temperature, and the concentration of the electrolyte solution. The type of cell determines the maximum possible voltage that can be delivered by the cell, while the temperature affects the chemical reactions inside the cell, which can affect the EMF. The concentration of the electrolyte solution also affects the EMF, as a higher concentration can lead to a greater voltage difference between the electrodes.

Why EMF is always greater than terminal voltage

Despite the factors that affect both EMF and terminal voltage, the EMF of a cell is always greater than its terminal voltage. This is due to the internal resistance of the cell, which causes a voltage drop when a device is connected to the cell. The EMF represents the maximum possible voltage that can be delivered by the cell, while the terminal voltage is the actual voltage that is delivered to the device. The internal resistance of the cell causes a voltage drop, reducing the terminal voltage, which is always less than the EMF.

Ohm’s Law

Ohm’s law states that the current flowing through a circuit is directly proportional to the voltage and inversely proportional to the resistance of the circuit. When a device is connected to a cell, the internal resistance of the cell causes a voltage drop, reducing the terminal voltage. This voltage drop is proportional to the amount of current flowing through the circuit, according to Ohm’s law. As the current increases, the voltage drop across the internal resistance of the cell also increases, reducing the terminal voltage.

Conservation of Energy

Another reason why the EMF of a cell is always greater than its terminal voltage is due to the conservation of energy. The EMF represents the maximum possible voltage that can be delivered by the cell, while the terminal voltage is the actual voltage that is delivered to the device. The difference between the EMF and terminal voltage represents the voltage drop across the internal resistance of the cell, which is converted into heat energy. This is due to the conservation of energy, which states that energy cannot be created or destroyed, only converted from one form to another.

FAQs for Why EMF of Cell is Always Greater than its Terminal Voltage

What is EMF and Terminal Voltage?

EMF stands for Electromotive Force, which is the force that drives the flow of electrical charge in a circuit. It is the maximum potential difference that can be developed between the two terminals of a cell when it is not delivering a current. On the other hand, terminal voltage is the potential difference between the two terminals of a cell when it is delivering a current.

Why is the EMF of a cell always greater than its terminal voltage?

The EMF of a cell is always greater than its terminal voltage because of the internal resistance of the cell. When a current flows through a cell, some of the electrical energy produced by the chemical reaction inside the cell is used to overcome the resistance of the cell’s internal components. This resistance reduces the potential difference across the terminals of the cell and results in a lower terminal voltage.

How does the internal resistance of a cell affect the terminal voltage?

The internal resistance of a cell affects the terminal voltage by causing a voltage drop across the cell’s internal components. This voltage drop reduces the potential difference between the two terminals of the cell and results in a lower terminal voltage. The amount of voltage drop depends on the amount of current flowing through the cell and the resistance of the cell’s internal components.

What happens when the current flowing through a cell increases?

When the current flowing through a cell increases, the voltage drop across the cell’s internal components increases. This results in a lower terminal voltage. However, the EMF of the cell remains the same because it is not affected by the internal resistance of the cell.

How can we measure the EMF of a cell and its terminal voltage?

The EMF of a cell can be measured using a potentiometer or a voltmeter connected across the cell’s terminals when it is not delivering a current. The terminal voltage can be measured using a voltmeter connected across the cell’s terminals when it is delivering a current. It is important to note that the terminal voltage will vary depending on the amount of current flowing through the cell.

Can the terminal voltage ever be higher than the EMF of a cell?

No, the terminal voltage of a cell can never be higher than its EMF. The EMF represents the maximum potential difference that can be developed between the two terminals of the cell, while the terminal voltage represents the potential difference that exists between the two terminals of the cell when it is delivering a current. The terminal voltage will always be lower than the EMF due to the internal resistance of the cell.