Does terminal potential of a cell is equal to emf?
2 Answers
Eddy currents have several applications in the medical field, primarily in diagnostic imaging and therapeutic techniques. Here are some key applications:
1. **Magnetic Resonance Imaging (MRI)**: Eddy currents are generated in the conductive materials of the MRI machine and the patient's body during the imaging process. Although they can cause artifacts in the images, understanding and controlling these currents help improve image quality and reduce distortions.
2. **Induction Heating**: In certain medical treatments, such as cancer therapy, eddy currents can be induced in tumor tissues to generate heat. This localized heating can help destroy cancer cells while minimizing damage to surrounding healthy tissue.
3. **Non-Destructive Testing**: Eddy current testing can be used to assess the integrity of medical devices, such as implants and surgical instruments, ensuring they are free of defects before use.
4. **Electromagnetic Compatibility Testing**: Eddy currents can be analyzed to evaluate how medical devices interact with magnetic fields, ensuring they operate safely around MRI machines and other magnetic equipment.
5. **Biological Research**: Eddy current techniques can be used in various research applications, such as studying the electrical properties of tissues and cellular interactions, contributing to the development of new medical technologies.
6. **Transcranial Magnetic Stimulation (TMS)**: Although primarily focused on magnetic fields rather than eddy currents, TMS utilizes magnetic stimulation to induce electrical currents in the brain, which can help in treating conditions like depression.
Overall, while eddy currents can present challenges in imaging, their manipulation offers significant benefits in treatment and diagnostics in the medical field.
1. **Magnetic Resonance Imaging (MRI)**: Eddy currents are generated in the conductive materials of the MRI machine and the patient's body during the imaging process. Although they can cause artifacts in the images, understanding and controlling these currents help improve image quality and reduce distortions.
2. **Induction Heating**: In certain medical treatments, such as cancer therapy, eddy currents can be induced in tumor tissues to generate heat. This localized heating can help destroy cancer cells while minimizing damage to surrounding healthy tissue.
3. **Non-Destructive Testing**: Eddy current testing can be used to assess the integrity of medical devices, such as implants and surgical instruments, ensuring they are free of defects before use.
4. **Electromagnetic Compatibility Testing**: Eddy currents can be analyzed to evaluate how medical devices interact with magnetic fields, ensuring they operate safely around MRI machines and other magnetic equipment.
5. **Biological Research**: Eddy current techniques can be used in various research applications, such as studying the electrical properties of tissues and cellular interactions, contributing to the development of new medical technologies.
6. **Transcranial Magnetic Stimulation (TMS)**: Although primarily focused on magnetic fields rather than eddy currents, TMS utilizes magnetic stimulation to induce electrical currents in the brain, which can help in treating conditions like depression.
Overall, while eddy currents can present challenges in imaging, their manipulation offers significant benefits in treatment and diagnostics in the medical field.
No, the terminal potential (or terminal voltage) of a cell is **not always equal** to the electromotive force (EMF) of the cell. There is a relationship between the two, but they differ depending on whether or not the cell is delivering current to an external circuit.
### Key Definitions:
1. **Electromotive Force (EMF)**:
- EMF is the maximum potential difference between the two terminals of a cell when no current is flowing. It is the energy provided by the cell per unit charge to drive the current around the circuit. In other words, it's the open-circuit voltage when the cell is not connected to any external load.
- Denoted by **E**.
- It represents the chemical energy converted into electrical energy per unit charge in the cell.
2. **Terminal Voltage**:
- Terminal voltage is the actual potential difference between the two terminals of a cell when it is connected to an external load and current is flowing.
- It is the voltage you measure across the cell's terminals when the circuit is complete.
- Denoted by **V**.
### Relationship Between Terminal Voltage and EMF:
#### 1. **When No Current Flows (Open Circuit):**
- In an open circuit, no current is flowing, and the terminal voltage is equal to the EMF.
- \[
V = E
\]
- Example: When a battery is not connected to any external device, the voltage measured across its terminals will be its EMF.
#### 2. **When Current Flows (Closed Circuit):**
- When the cell is delivering current to a circuit, internal resistance comes into play. Every real battery or cell has some **internal resistance (r)**, which resists the flow of current inside the cell itself.
- Due to the internal resistance, some voltage is "lost" within the cell as heat, and this causes the terminal voltage to be less than the EMF.
- The relationship is given by:
\[
V = E - Ir
\]
Where:
- \(V\) is the terminal voltage.
- \(E\) is the EMF.
- \(I\) is the current flowing through the circuit.
- \(r\) is the internal resistance of the cell.
- In this case, the terminal voltage is lower than the EMF because some energy is used to overcome the internal resistance.
#### 3. **When the Cell is Being Charged:**
- If the cell is being charged (current flows into the cell), the terminal voltage can be **greater than the EMF**. This is because the charging current adds to the internal voltage drop.
- The relationship during charging is:
\[
V = E + Ir
\]
### Example Scenario:
- Consider a battery with an EMF of 12 V and an internal resistance of 0.5 ohms.
- **Open Circuit**: If no current is flowing, the terminal voltage will be 12 V (same as the EMF).
- **Closed Circuit**: If the battery delivers a current of 2 A to a circuit, the terminal voltage can be calculated as:
\[
V = E - Ir = 12 - (2 \times 0.5) = 12 - 1 = 11 \text{ V}
\]
So, in this case, the terminal voltage drops to 11 V when the battery is supplying current.
### Summary:
- **Terminal voltage = EMF only when no current flows (open circuit).**
- **Terminal voltage < EMF when the cell is delivering current (closed circuit) due to internal resistance.**
- **Terminal voltage > EMF when the cell is being charged.**
In practical situations, terminal voltage is usually less than the EMF when a battery is in use, as current flowing through the battery causes some voltage to drop across the internal resistance.
### Key Definitions:
1. **Electromotive Force (EMF)**:
- EMF is the maximum potential difference between the two terminals of a cell when no current is flowing. It is the energy provided by the cell per unit charge to drive the current around the circuit. In other words, it's the open-circuit voltage when the cell is not connected to any external load.
- Denoted by **E**.
- It represents the chemical energy converted into electrical energy per unit charge in the cell.
2. **Terminal Voltage**:
- Terminal voltage is the actual potential difference between the two terminals of a cell when it is connected to an external load and current is flowing.
- It is the voltage you measure across the cell's terminals when the circuit is complete.
- Denoted by **V**.
### Relationship Between Terminal Voltage and EMF:
#### 1. **When No Current Flows (Open Circuit):**
- In an open circuit, no current is flowing, and the terminal voltage is equal to the EMF.
- \[
V = E
\]
- Example: When a battery is not connected to any external device, the voltage measured across its terminals will be its EMF.
#### 2. **When Current Flows (Closed Circuit):**
- When the cell is delivering current to a circuit, internal resistance comes into play. Every real battery or cell has some **internal resistance (r)**, which resists the flow of current inside the cell itself.
- Due to the internal resistance, some voltage is "lost" within the cell as heat, and this causes the terminal voltage to be less than the EMF.
- The relationship is given by:
\[
V = E - Ir
\]
Where:
- \(V\) is the terminal voltage.
- \(E\) is the EMF.
- \(I\) is the current flowing through the circuit.
- \(r\) is the internal resistance of the cell.
- In this case, the terminal voltage is lower than the EMF because some energy is used to overcome the internal resistance.
#### 3. **When the Cell is Being Charged:**
- If the cell is being charged (current flows into the cell), the terminal voltage can be **greater than the EMF**. This is because the charging current adds to the internal voltage drop.
- The relationship during charging is:
\[
V = E + Ir
\]
### Example Scenario:
- Consider a battery with an EMF of 12 V and an internal resistance of 0.5 ohms.
- **Open Circuit**: If no current is flowing, the terminal voltage will be 12 V (same as the EMF).
- **Closed Circuit**: If the battery delivers a current of 2 A to a circuit, the terminal voltage can be calculated as:
\[
V = E - Ir = 12 - (2 \times 0.5) = 12 - 1 = 11 \text{ V}
\]
So, in this case, the terminal voltage drops to 11 V when the battery is supplying current.
### Summary:
- **Terminal voltage = EMF only when no current flows (open circuit).**
- **Terminal voltage < EMF when the cell is delivering current (closed circuit) due to internal resistance.**
- **Terminal voltage > EMF when the cell is being charged.**
In practical situations, terminal voltage is usually less than the EMF when a battery is in use, as current flowing through the battery causes some voltage to drop across the internal resistance.