Electrical Engineering: Basic Concepts (5 of 7) Voltage

Summary

This educational video delves into the concept of voltage, illustrating it with the example of a capacitor with charged plates. It explains that voltage is the work required to move a charge against an electric field, from one plate to another. The video simplifies the idea by defining voltage as the potential difference between two points, emphasizing that it represents the force or 'push' that drives the flow of charge in a circuit. It concludes by cautioning that high voltages can be dangerous due to their strong force.

Takeaways

• 🔋 Voltage is the amount of work required to move a charge against an electric field.
• ⚡ The electric field is established between two charged plates, directed from positive to negative charge.
• 💡 The work needed to move a charge is influenced by the electric field's strength and the distance between the charges.
• 🔗 The definition of voltage is the work done to move a unit charge through an electric field, expressed as joules per coulomb (J/C).
• 🔄 Voltage is also described as the potential difference between two points, indicating the force that pushes charges through a circuit.
• 🔄 A volt is defined as the amount of work (joules) needed to move one coulomb of charge.
• 🔌 When discussing voltage across a battery, we refer to the potential difference between its positive and negative terminals.
• 📉 The potential difference can be expressed as the voltage at one point minus the voltage at another, indicating the relative 'height' of electrical potential.
• ⚠️ High voltages can be dangerous as they represent a significant force that can push charges, potentially causing harm if contacted.
• 🔧 Voltage is often symbolized as electromotive force (EMF), highlighting its role as the driving force that pushes charges through an electrical circuit.

Q & A

What is the basic concept of voltage?

Voltage is the potential difference between two points in an electric field, which represents the force or push that causes charges to move through a circuit.

How is the electric field related to voltage?

The electric field is the force field that exists between positive and negative charges, and voltage is the potential difference that exists due to this field, which requires work to move a charge against this field.

What is the formula for calculating the work done to move a charge across an electric field?

The work done (W) is calculated by the formula W = F * d, where F is the force required to move the charge and d is the distance over which the charge is moved.

How is force related to the strength of the electric field and the charge?

The force (F) experienced by a charge is the product of the charge's size (Q) and the strength of the electric field (E), expressed as F = Q * E.

What is the definition of voltage in terms of work and charge?

Voltage (V) is defined as the work done (W) to move a charge (Q) across an electric field, divided by the size of the charge, V = W / Q.

Why is the size of the charge (Q) canceled out in the voltage formula?

The charge (Q) is canceled out in the voltage formula because the definition of voltage is the ratio of work done to the charge, and this ratio remains constant regardless of the size of the charge.

What is the significance of a volt as a unit of measurement?

A volt is a unit of electric potential difference, defined as the amount of work (in joules) done to move one coulomb of charge against an electric field.

How is voltage related to the potential difference or electromotive force (EMF)?

Voltage is synonymous with potential difference and electromotive force, representing the force that pushes charges through a circuit, with larger voltages indicating a greater push.

Why can high voltages be dangerous?

High voltages can be dangerous because they represent a large potential difference that can push charges, including through a person's body, potentially causing harm.

What does it mean when we say the voltage at point A is 10 volts higher than at point B?

It means that there is a potential difference of 10 volts between points A and B, indicating that it would require 10 joules of work to move one coulomb of charge from point B to point A.

Outlines

00:00

🔋 Understanding Voltage

The video begins by explaining the concept of voltage using the analogy of a capacitor with positively and negatively charged plates separated by a distance D. An electric field exists between these charges, directing from positive to negative. A small positive charge placed on the positive side is attracted to the negative side and repelled from the positive side. The work required to move this charge from one side to the other against the electric field is proportional to the charge's size and the electric field's strength. Work is defined as the force (charge times electric field strength) times the distance D. Voltage is introduced as the work done to move a charge across a distance in an electric field, divided by the charge's size. This ratio remains constant regardless of the charge's magnitude. Voltage is thus the potential difference between two points, calculated as the electric field's strength times the distance between the points. The concept of a volt (joule per coulomb) is also explained, emphasizing that one volt is the work required to move one coulomb of charge through an electric field.

05:01

🚀 Voltage as Electromotive Force

The second paragraph delves into the practical implications of voltage, describing it as the force or 'push' that drives the movement of charges through a circuit. Voltage is likened to the electromotive force (EMF), which is the energy provided by a power source to move charges. The paragraph emphasizes that a higher voltage difference across a battery results in a greater 'push' for the charges, making them move more vigorously through the circuit. This push is what facilitates the flow of current. The paragraph concludes by cautioning that very large voltages can be dangerous, as the strong force can potentially harm if it pushes charges through a person's body, illustrating the importance of understanding and handling voltage safely.

Keywords

💡Voltage

Voltage, in the context of the video, refers to the electric potential difference between two points. It is the force that pushes electric charges through an electric circuit. The video explains that voltage is analogous to the work required to move a charge against an electric field, which is defined as the work done per unit charge. For instance, if it takes one joule of work to move one coulomb of charge from one point to another, the voltage between those points is one volt.

💡Electric Field

The electric field is a vector quantity that describes the force exerted on a unit charge in an electric charge's presence. In the video, the electric field is depicted as existing between a positively and negatively charged capacitor plate, directing from the positive charge to the negative charge. This field is what causes a force on a charge placed within it, as illustrated when a small positive charge is attracted towards the negative plate.

💡Capacitor

A capacitor is an electronic component that stores electrical energy in an electric field. The video uses a capacitor plate setup to explain the concept of voltage, where one plate is positively charged and the other negatively charged, creating an electric field between them. The capacitor serves as a practical example to demonstrate how voltage arises from the separation of charge.

💡Work

In the video, work is defined in the context of physics as the product of the force applied to an object and the distance the object moves in the direction of the force. Specifically, it relates to the work done to move a charge through an electric field, which is used to define voltage. The video states that the work done (W) is equal to the force (F) times the distance (d), and in the case of moving a charge, it's the charge (Q) times the electric field strength (E) times the distance (d).

💡Charge

Charge, in the video, refers to the property of matter that causes it to experience a force when placed in an electromagnetic field. It is measured in coulombs (C). The video uses the concept of charge to explain how voltage is the work done per unit charge, emphasizing that the voltage remains constant regardless of the size of the charge moved.

💡Potential Difference

Potential difference is synonymous with voltage and is the term used to describe the difference in electric potential between two points in an electric circuit. The video explains that voltage can be thought of as the potential difference, which is the amount of work needed to move a unit charge from one point to another against the electric field.

💡Electromotive Force (EMF)

EMF, or electromotive force, is the term used to describe the voltage provided by a source such as a battery. The video mentions EMF to convey that voltage is the force or 'push' that drives electric charges through a circuit. It's the reason why a battery can cause current to flow when connected to a load.

💡Coulomb

The coulomb is the unit of electric charge and is used to quantify the amount of charge. In the video, the coulomb is used in the context of calculating the work done to move a charge through an electric field, which is essential for defining voltage. The video clarifies that voltage is independent of the actual amount of charge moved, as the ratio of work to charge remains constant.

💡Joule

The joule is the unit of energy or work in the International System of Units (SI). The video uses joules to describe the amount of work done when moving a charge through an electric field. It explains that one volt is equivalent to one joule per coulomb, emphasizing the relationship between voltage, work, and charge.

💡Potential

Potential, in the context of the video, refers to the electric potential, which is the amount of work that can be done by an electric charge in an electric field. It is related to voltage and is used to describe the energy available to do work at a point in an electric field. The video explains that voltage is the difference in electric potential between two points.

Highlights

Voltage is the work done to move a charge across an electric field.

The electric field is directed from a positively charged plate to a negatively charged one.

Moving a charge against an electric field requires a certain amount of work.

The force required is proportional to the charge size and the electric field strength.

Work done is calculated as the force required times the distance over which the charge is moved.

Voltage is defined as the work done per unit charge.

The ratio of work done to charge size remains constant regardless of the charge's magnitude.

Voltage can be thought of as the potential difference between two points in an electric field.

A volt is defined as one joule per coulomb of charge.

The voltage difference represents how much more volts one point has compared to another.

Voltage difference is calculated as the voltage at one point minus the voltage at another.

The electromotive force (EMF) is another term for voltage, representing the force that pushes charges.

Voltage represents the force or push that charges feel in a circuit.

A larger voltage difference results in a greater push for charges to move through the circuit.

High voltages can be dangerous as they can push charges through the body causing harm.

Voltage is the driving force that pushes charge through circuits.

Transcripts

welcome to electron line in this video

we're going to talk about voltage what

does voltage mean well the basic concept

comes from this let's say we have a

capacitor plate set on one side we have

a positively charged capacitor plate on

the other side we have a negatively

charged capacitor plate and let's say

that they're apart a distance D from one

another we then realize there's an

electric field that exists between the

positive negative charges the electric

field will be directed from the positive

charge to the negative

charge if we now place a small charge a

positive charge on the on the right side

of this

capacitor we then realize that it's

being attracted towards the negative

charge here and being repelled by the

positive charge there so if you want to

move that charge from the right side to

the left side then it's going to require

a certain amount of work a certain

amount of force to get it there the

amount of force required is equal to the

size of that charge in kums times the

the strength of the electric field the

stronger the field the greater the

disparity of charges the more Force

you're going to need to push that charge

across the work is defined by the force

required times the distance so if we

push that charge all the way over to the

other side through a distance D the

amount of work we've done is equal to

the force time D and the force that that

charge experience is the size of the

charge time the strength of the electric

field so it's Q * Z * d That's the work

done now the definition of voltage

voltage is defined as the amount of work

done to move a charge

across this distance here where there's

an electric field the amount of work

done to do that divided by the size of

the charge that makes sense because

let's say that the charge was twice as

big let's say we have two Q

there so let's say we have twice a

charge it would then require twice the

force twice the charge therefore twice

the work and we will have twice the

charge and you see that that ratio will

always be the same regardless as to the

size of the charge that we use so it's

always the ratio of the amount of work

done divided by the charge used and

regardless how big we make that charge

that ratio is always the same and that

is then defined as the voltage is the

work done to get a charge across from

the left side to the right or from the

right side to the left side in this case

from the negative charge to the positive

charge through an electric

field divided by the charge required

if we plug in if we get rid of these

twos again right here if we plug in what

work is equal to we can see that the

work is equal to Q E * d ided by the

charge Q The Q's cancel out which means

that the voltage then is defined as to

the strength of the electric field times

the distance between the left side and

the right side of that field the voltage

can be thought of in two ways it's equal

to the amount of work we need to do to

get a charge moved through an electric

field divided by the size of the charge

or simply the potential difference or

voltage is equal to the strength of the

electric field times the

distance now a volt is defined therefore

as a jewel per Kum remember it's work

over charge work is in Jewels charge is

in kums so a volt is defined as a jewel

per Kum in other words if we have a one

Kum of

charge and it takes one Jewel of work to

get it across that means that the

voltage between those two plates is

equal to one volt that's how we want to

look at it if we have a battery and we

have a positive end of the battery and

we have a negative end of the battery

and the Volt across the battery is 10

volts we can say that the voltage at a

is 10 volts higher than the voltage at B

so sometimes we talk about potential

difference or voltage difference it is

how much more volts we have on one side

compared to the other side this case a

is 10 volt higher than than b b could be

100 volts then a would be at 110 volts

whenever we talk about the voltage of a

battery we really talk about the

difference in the voltage or the

potential difference this case when we

talk about volts from A to B that is

equal to volts at a minus volt at B

since a is bigger than b it'll be 10

volt minus 0 volt which is a 10 volt

difference but if we talk about VBA this

is equal to V at B minus V at a which is

equal to 0 Vol - 10 Vol is equal to - 10

Vol when we go from B to a we increase

in voltage by 10 volts if we go from A

to B we decrease by 10 volts that's a

negative voltage

direction another way of looking at

voltage V voltage is equal to the

potential difference potential

difference means the voltage difference

between two points on the circuit

sometimes it's also called the EMF or

the electromotive force and one of the

reasons reasons why we think about it as

the electromotive force is because

voltage is really the amount of volts

you have on a circuit or in a battery

determines how much push charges field

to move through the circuit so another

way of looking at voltage is to say that

the voltage represents the force or push

charges feel of course charges don't

really feel anything but if you think

about it if you're a charge and there's

a voltage difference there you're going

to feel a push to the circuit is going

to feel as if you're being pushed

through that circuit by the voltage

difference the bigger the voltage

difference the bigger the voltage across

that battery the more push that charge

is going to feel the greater the voltage

the greater the force that the or the

push that the that the charges feel

inside the circuit the bigger the

potential difference the greater the

force the more push to get the charges

around the circuit and that's why very

large voltages can be very dangerous

because large pushes can actually become

dangerous when get near that charges may

get push through your body if you get if

you touch a circuit and if the potential

difference of the voltage is very large

again voltage think of it as that thing

that pushes charge through circuits the

bigger the voltage the bigger the push

and that's a good place to

start