Current & Potential Difference | Electricity | Physics | FuseSchool

Summary

This video covers the relationship between current, resistance, and potential difference (voltage), demonstrating how to calculate resistance using Ohm's law (V = IR). It explains the measurement of potential difference across components using a voltmeter in parallel and current with an ammeter in series. The video walks through practical examples, highlighting how to rearrange the equation to solve for current and resistance. By the end, viewers understand the importance of these electrical concepts, how to use voltmeters and ammeters, and how to apply Ohm's law to calculate electrical values.

Takeaways

• 💡 Potential difference, also known as voltage, is essential to make a current flow across an electrical component.
• 🔋 Cells or batteries provide the potential difference required for current flow in a circuit.
• 📏 Ohm's law links potential difference (V), current (I), and resistance (R) using the equation V = IR.
• ⚡ Voltage is measured in volts (V), current is measured in amperes (A) or capital I, and resistance is measured in ohms (Ω) represented by R.
• 🔄 The V = IR equation can be rearranged to find either current, voltage, or resistance depending on the values provided.
• 🔧 A voltmeter is used to measure potential difference and must be connected in parallel with the component being measured.
• 🔌 An ammeter is used to measure current and is connected in series with the component.
• 🧮 To calculate resistance, both current and voltage must be measured, and values substituted into the V = IR equation.
• 📝 A worked example showed that rearranging the formula to I = V/R gave a current of 0.3 amps.
• 📚 The summary emphasized the key concepts of voltage, current, resistance, and how to measure and apply them using Ohm's law.

Q & A

What is the relationship between current, resistance, and potential difference?

Ohm's law states that the potential difference (voltage) is equal to the current multiplied by the resistance, expressed as V = I × R.

What is potential difference also known as, and why is it important?

Potential difference is also known as voltage. It is important because it is required to make a current flow across an electrical component.

How do cells or batteries contribute to a circuit?

Cells or batteries provide the potential difference (voltage) needed to make a current flow in the circuit.

What are the units for potential difference, current, and resistance?

Potential difference (voltage) is measured in volts (V), current is measured in amperes (A), and resistance is measured in ohms (Ω).

How do you rearrange the formula V = I × R to find the current?

To find the current (I), rearrange the formula to I = V ÷ R, which means current is equal to the potential difference divided by the resistance.

How is the potential difference measured across a component in a circuit?

Potential difference is measured using a voltmeter, which must be connected in parallel with the component you are measuring.

How is current measured in a circuit?

Current is measured using an ammeter, which should be connected in series (in line) with the component to measure the current.

What is the correct setup if you want to measure both current and potential difference in a circuit?

To measure both, place the ammeter in series with the component and the voltmeter in parallel with the component.

How can you calculate resistance once you know the current and potential difference?

Once you have measured the current and the potential difference, you can substitute these values into the equation V = I × R to solve for resistance (R = V ÷ I).

What is the resistance of a lamp if the potential difference is 1.5 volts and the current is 1 amp?

The resistance would be 1.5 ohms, calculated using the formula R = V ÷ I.

Outlines

00:00

⚡ Understanding the Relationship Between Current, Resistance, and Voltage

This paragraph introduces the concept of how current relates to both resistance and potential difference (voltage). It explains that a voltage is necessary for a current to flow through a component, with cells or batteries typically providing this potential difference. Ohm's Law is introduced as the key equation that relates voltage, current, and resistance (V = I × R), and the paragraph highlights that voltage is measured in volts (V), current in amperes (A), and resistance in ohms (Ω).

🔍 Ohm's Law and Rearranging the Equation

Here, the focus shifts to Ohm's Law and how to manipulate its equation. The video prompts the viewer to rearrange the formula to solve for current (I = V ÷ R). An example is given, encouraging viewers to pause and calculate the current based on provided values. This section reinforces the ease of substituting values into the V = IR equation to determine unknown variables like current, voltage, or resistance.

💡 Measuring Potential Difference and Current in a Circuit

This section introduces the method of measuring potential difference (voltage) across components in a circuit using a voltmeter. The voltmeter must be connected in parallel with the component being measured. It further explains that to measure current, an ammeter should be connected in series with the component. This clear distinction between parallel and series connections is emphasized for accurate measurements.

🔗 Using Circuit Measurements to Calculate Resistance

In this paragraph, the process of measuring both current and potential difference to calculate resistance is explained. The user is instructed to set up a circuit with both an ammeter in series and a voltmeter in parallel, allowing for the use of the V = IR equation to find the resistance across a component, such as a lamp in this example.

📊 Practice Questions and Conclusion

The final paragraph summarizes key takeaways, including the relationship between voltage, current, and resistance as stated by Ohm's Law. Viewers are prompted to solve two practice questions and check their answers, reinforcing their understanding of the concepts. The video concludes by thanking viewers for watching and reiterating the core lesson of how to measure and calculate electrical properties in circuits.

Keywords

💡Current

Current refers to the flow of electric charge through a conductor. It is measured in amperes (A) and represented in equations by the symbol 'I'. In the video, current is described as flowing through components when a potential difference (voltage) is applied, with examples of measuring current using an ammeter.

💡Resistance

Resistance is the opposition to the flow of current in an electrical circuit. It is measured in ohms (Ω) and represented by the symbol 'R'. The video explains how resistance affects current and voltage, and how it can be calculated using Ohm’s Law (V = IR).

💡Potential Difference (Voltage)

Potential difference, also called voltage, is the force that pushes electric current through a circuit. It is measured in volts (V) and denoted by the symbol 'V'. In the video, potential difference is necessary for current to flow and can be measured using a voltmeter, which must be connected in parallel to the component.

💡Ohm’s Law

Ohm’s Law describes the relationship between voltage (V), current (I), and resistance (R) in a circuit, stating that V = IR. The video demonstrates how this equation can be used to calculate one variable if the other two are known, with practical examples of rearranging the equation to find current or resistance.

💡Voltmeter

A voltmeter is a device used to measure the potential difference (voltage) across a component. In the video, it is emphasized that the voltmeter must be connected in parallel with the component being measured, such as the lamp, to correctly display the voltage.

💡Ammeter

An ammeter is an instrument used to measure the current in a circuit. It is connected in series with the component being measured, as shown in the video where the ammeter is placed in line with the lamp to measure the current.

💡Circuit

A circuit is a closed loop that allows current to flow, powered by a potential difference from sources like batteries. The video describes how different components such as lamps and meters (voltmeter and ammeter) are connected in circuits to measure current and voltage.

💡Parallel Connection

A parallel connection refers to the arrangement of components in a circuit where the voltmeter is connected across two points to measure the voltage. The video stresses that voltmeters must always be connected in parallel with the component, such as a lamp, to measure potential difference accurately.

💡Series Connection

A series connection involves connecting electrical components end-to-end so that the same current flows through each component. The video explains that the ammeter is connected in series with the component being measured, ensuring accurate current measurements.

💡V = IR

This is the mathematical representation of Ohm’s Law, which shows that voltage (V) is the product of current (I) and resistance (R). The video uses this equation in several examples to show how to calculate current, voltage, or resistance by rearranging and substituting values into the formula.

Highlights

Introduction to how current relates to both resistance and potential difference.

Explanation of how potential difference (voltage) is needed across an electrical component to make a current flow.

Cells or batteries provide the potential difference necessary to make a current flow.

Introduction to Ohm's Law: Voltage (V) is equal to the current (I) multiplied by the resistance (R), expressed as V = IR.

Potential difference or voltage is measured in volts (V), and current is measured in amperes (A), denoted by capital I.

Resistance is measured in ohms, symbolized by Ω, and represented by the letter R in equations.

Equation V = IR can be rearranged to solve for different variables (current, resistance, or voltage) depending on the given values.

To calculate current, rearrange Ohm's Law to I = V/R.

Potential difference across components is measured using a voltmeter, which must be connected in parallel with the component.

Ammeter is used to measure current and must be connected in series with the component.

Combining both the voltmeter and ammeter allows for measuring both the current and potential difference, which can be used to calculate resistance.

In the example given, the resistance across a lamp was calculated as 1.5 ohms.

Practical question: After measuring the current and potential difference, users are asked to calculate resistance and verify their answer.

In summary, the video reviewed the relationship between voltage, current, and resistance, and demonstrated how to measure them.

Final questions encourage viewers to apply what they’ve learned by calculating voltage and resistance based on given values.

Transcripts

hello everyone today we will be looking

at how current relates to both

resistance and potential difference and

how we record the potential difference

in currents across different components

to then calculate resistances a

potential difference is also known as a

voltage a potential difference or

voltage is needed across an electrical

component to make a current flow

cells or batteries often provide this

potential difference

ohm's law tells us how potential

difference current and resistance are

related

potential difference or voltage is

measured in volts v and is shown by the

symbol v

current is measured in amperes and is

described in equations by capital i

this originally comes from the french

phrase intensity decline meaning current

intensity resistance is measured in ohms

which are shown using this symbol and

sensibly is represented by a capital

r these three things are linked together

in an equation which states that the

voltage is equal to the resistance

multiplied by the current or simply v

equals i times r this equation can be

rearranged in a manner of ways and is

best represented by the triangle

pause the video and give it a go

did you get 0.3 amps

we're trying to find the current so we

need to rearrange the v equals ir

equation to see that current is the

potential difference divided by the

resistance

see it's very easy substituting values

into the v equals ir equation

so now let's have a look at how to

measure the potential difference across

different components

earlier we said that a potential

difference is needed to make a current

flow and that batteries or cells often

provide this potential difference

let's have a look at how we can measure

the potential difference across the lamp

in this circuit

we measure potential differences using a

voltmeter

this voltmeter must be connected in

parallel with the component we're

measuring across

so here it's in parallel with the lamp

then simply read what the voltmeter says

1.5

volts so the voltmeter goes in parallel

and measures the potential difference

if we wanted to measure the current

see how we instead used an ammeter and

the ammeter is connected in series so in

a line with the component what if we

wanted to measure both the current and

the potential difference

simply set up a circuit with an ammeter

in series and a voltmeter in parallel

once we've measured the current and the

potential difference we can then use

these values and substitute them into

our v equals ir equation to find the

resistance

so what's the resistance across this

lamp

pause the video and work it out

did you get 1.5 ohms

here are two more questions for you to

give a go pause the video work them out

and click play when you're ready to

check your answers

did you get them right 5.4 volts and 20

ohms

in summary we have learned that the

voltage is equal to the current

multiplied by the resistance

and how to measure the potential

difference and the current across

components

thanks for watching

you