Electromotive Force

Ryan Pitcher

26 Aug 201302:52

Summary

TLDRThis video script explains the concept of electromotive force (EMF), which is the potential difference that drives electric current in a circuit. It highlights that EMF can be generated through various methods, with batteries being a common example. The script discusses how unloaded voltage, the potential difference across open terminals, changes when a circuit is connected due to internal resistance, causing a voltage drop. It also demonstrates this with a DC power supply, which initially has an unloaded voltage of 5 volts but drops to 4.7 volts when in use. The video aims to educate viewers on the fundamental forms of electricity generation and the role of EMF in practical applications.

Takeaways

🔋 Electrical charges create a field that repels or attracts other charges based on their polarity.
⚡ Electromotive force (EMF) is the potential difference that causes electric current to flow, measured in volts.
🔌 The symbols 'E' or 'V' are commonly used to represent electromotive force.
🔋 There are seven fundamental forms of electricity generation, all creating an EMF.
🔬 Electrochemical reactions, like those in a battery, are a common source of EMF.
🔌 The unloaded voltage is the potential difference across two open terminals of an EMF source.
🔌 When a circuit is connected, the voltage across the EMF source drops due to internal resistance.
🔌 A 1.5-volt battery, when unloaded, shows a voltage drop to 1.3 volts when a circuit is connected.
🔌 DC power supplies can generate various levels of EMF, with 5 volts being a set unloaded voltage.
🔌 The internal resistance of a DC power supply reduces the applied circuit voltage when current flows, as seen with a drop from 5 to 4.7 volts.
⚡ EMF is essential for driving current in a circuit, and its sources and practical applications were discussed.

Q & A

What generates an electric field around them?
-Electrical charges generate an electric field around them.
How do like charges and opposite charges interact in an electric field?
-Like charges repel each other, while opposite charges attract each other.
What is the term for a potential difference measured in volts?
-Electromotive force (EMF) is the term used for a potential difference measured in volts.
What are the common symbols used for electromotive force?
-The common symbols used for electromotive force are 'E' or 'V'.
What is the unloaded voltage and how is it related to the electromotive force?
-The unloaded voltage is the potential difference across two open terminals of an EMF source, which is the electromotive force when no current is flowing.
What causes a voltage drop when a circuit is connected to an EMF source?
-A voltage drop occurs when a circuit is connected to an EMF source due to the internal resistance of the EMF source and the components in the circuit.
How does the internal resistance of an EMF source affect the voltage when current flows?
-The internal resistance of an EMF source causes a reduction in the applied circuit voltage when current starts to flow, resulting in a voltage drop.
What is the unloaded voltage rating of a typical battery mentioned in the script?
-The unloaded voltage rating of a typical battery mentioned in the script is 1.5 volts.
What is the unloaded voltage setting of a DC power supply as per the script?
-The unloaded voltage setting of a DC power supply mentioned in the script is 5 volts.
How does the internal resistance of a DC power supply affect the applied circuit voltage?
-The internal resistance of a DC power supply reduces the applied circuit voltage when the circuit is connected and current starts to flow, causing a loss of potential difference.
What is the role of electromotive force in a circuit?
-Electromotive force is the potential difference that forces current to flow in a circuit, driving the flow of electrons through the components.

Outlines

00:00

🔋 Electromotive Force (EMF) Basics

The paragraph introduces the concept of electromotive force (EMF), which is the potential difference that drives electric current in a circuit. It explains how electrical charges create fields that interact with other charges, leading to repulsion or attraction. The paragraph also distinguishes between like and opposite charges and their effects. EMF is measured in volts and symbolized by 'e' or 'V'. The text further discusses the seven fundamental forms of electricity generation, all of which create an EMF. A common example is the electrochemical reaction found in batteries. The paragraph explains that when a potential difference is created by separating charged particles, an EMF is generated. It also details how the unloaded voltage of a battery, which is the potential difference across its open terminals, changes when a circuit is connected, leading to a voltage drop due to internal resistance. An example is given where a battery's unloaded voltage is 1.5 volts, but when connected to a circuit, it drops to 1.3 volts due to internal resistance. The paragraph concludes by discussing the DC power supply, another source of EMF, which can be adjusted to create different voltages. It also notes the unloaded voltage of a power supply and how it decreases when a circuit is connected due to internal resistance.

Mindmap

Keywords

💡Electrical charges

Electrical charges refer to the fundamental property of matter that causes it to experience a force when placed in an electromagnetic field. In the context of the video, electrical charges generate fields of force that can repel or attract other charged particles. This is the basis for the electromagnetic interactions that are central to the theme of the video.

💡Fields of force

Fields of force, also known as electric fields, are the influence exerted by an electric charge that can cause a force on other charges in its vicinity. The video explains that these fields are responsible for the repulsion between like charges and attraction between opposite charges, which is a fundamental concept in understanding electromagnetism.

💡Electromotive force (EMF)

Electromotive force, abbreviated as EMF, is the potential difference that causes current to flow in an electrical circuit. The video emphasizes that EMF is measured in volts and is what drives the flow of electric current. It is a key concept in the video as it is the force that initiates and sustains electrical activity.

💡Potential difference

A potential difference is the difference in electric potential energy between two points in an electric field. The video mentions that when enough charged particles are separated, a potential difference is created, which is the driving force behind the flow of electric current.

💡Voltage

Voltage, symbolized as 'V', is the electric potential difference between two points. The video uses the term to describe the unloaded voltage of a battery or power supply, which is the potential difference when no current is flowing. Voltage is a critical factor in determining the behavior of electrical circuits.

💡Electrochemical reaction

An electrochemical reaction is a chemical reaction that involves the transfer of electrons between molecules and ions, leading to an electrical current. The video specifically mentions batteries as an example of electrochemical reactions, where the potential difference across two open terminals is known as the unloaded voltage.

💡Unloaded voltage

Unloaded voltage is the voltage of an electrical source when it is not connected to a load or circuit. The video provides an example where a battery has an unloaded voltage rating of 1.5 volts, indicating the potential difference when it is not in use.

💡Internal resistance

Internal resistance is the resistance offered by the source of EMF itself, which can cause a voltage drop when current flows. The video illustrates this with a DC power supply, where the internal resistance reduces the applied circuit voltage when the circuit is connected and current starts to flow.

💡DC power supply

A DC power supply is a device that provides a direct current (DC) to an electrical circuit. The video explains that it can create different amounts of electromotive force, and it is used to demonstrate how the potential difference changes with varying voltage settings.

💡Circuit

A circuit is a closed loop through which electric current can flow. The video discusses how when a circuit is attached to a source of EMF, current flows, and there is typically some amount of resistance in all electrical components, leading to a voltage drop due to internal resistance.

💡Resistance

Resistance is the opposition to the flow of electric current in a circuit. The video touches on the concept that all electrical components and devices have some amount of resistance, which affects the voltage across the terminals of the source of EMF when current flows.

Highlights

Electrical charges generate a field that repels or attracts other charged particles.

Like charges repel, while opposite charges attract.

Electromotive force (EMF) is a potential difference measured in volts.

Common symbols for electromotive force are E or V.

EMF is the potential difference that forces electric current to flow.

There are seven fundamental forms of electricity generation, all creating an EMF.

Electrochemical reactions, like in a battery, are a common form of electricity generation.

The potential difference across two open terminals is known as the unloaded voltage.

Resistance in electrical components affects the voltage across the terminals of an EMF source.

When current flows, the voltage across the terminals of an EMF source is reduced due to internal resistance.

A battery with an unloaded voltage rating of 1.5 volts may have a reduced applied circuit voltage of 1.3 volts when in use.

DC power supplies can create different amounts of electromotive force.

An unloaded voltage of 5 volts may be reduced to 4.7 volts due to internal resistance when a circuit is connected.

Electromotive force is essential for the flow of current in a circuit.

Practical applications of EMF include various sources and devices used to generate electricity.