Current Electricity
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Understanding Electric Current
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Welcome, class! Today, we will start with the concept of electric current. Electric current (I) is defined as the rate of flow of electric charge through a conductor. Can anyone tell me the formula for current?
Is it I = Q/t, where Q is the charge and t is time?
Exactly! The SI unit for current is the Ampere (A). Also, it's important to note that conventional current flows from the positive to the negative terminal, which is opposite to the actual flow of electrons. Does anyone know why we use the conventional direction?
I think it's because early physicists defined it that way before the discovery of the electron!
Correct! You all are doing great. Let's remember this with the acronym 'ICu' – 'I' for Current and 'Cu' for 'Charge per unit time'.
Ohm's Law
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Now, let’s dive into Ohm’s Law, which states that the voltage across a conductor is directly proportional to the current flowing through it. The formula is V = I * R. Can anyone explain what each symbol represents?
V is voltage, I is current, and R is resistance!
Great! This law helps us understand how resistors work in circuits. For ohmic conductors, the V-I graph is a straight line. Why do you think that is?
Because the relationship is linear when temperature stays constant?
Exactly correct! Let's visualize this with the mnemonic 'VIR' – Voltage, Current, Resistance. You'll remember that these three are interconnected!
Resistance and Resistivity
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Next up is the concept of resistance and resistivity. Resistivity (ρ) is a material's resistance for a unit length and area. The formula is R = ρ (l/A). Can anyone explain what each variable means?
R is resistance, ρ is resistivity, l is the length of the conductor, and A is its cross-sectional area.
Exactly! This means a longer, thinner wire has more resistance. Also, remember that resistivity depends on the material and temperature. Can anyone give me an example of how temperature affects resistance?
In conductors, like metals, resistance increases with temperature.
Spot on! Remember this with the phrase 'Hotter means Higher resistance'! Let's summarize: resistivity determines how well materials conduct electricity.
Kirchhoff’s Rules
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Finally, let’s cover Kirchhoff’s Rules. We have Kirchhoff’s Current Law (KCL) and Kirchhoff’s Voltage Law (KVL). KCL states that the total current entering a junction equals the total current leaving it. Does anyone know why this is important?
Because it helps in analyzing complex circuits!
Correct! KVL states that the sum of the potential differences in a closed loop equals zero. Why is this useful?
It helps in simplifying circuit calculations.
"Exactly right! To help remember, think of the acronym 'KCL and KVL – Current and Voltage Sum Up!'"<img id="dimg_GEQ_aNv0KsXEp84P4_SIgQg_17" 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" 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Practical Applications
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To wrap up, let’s discuss some practical applications of what we've learned, such as the Wheatstone bridge. What is its purpose?
It's used to measure unknown resistances!
Exactly! And the potentiometer can measure EMF accurately. How does it compare to a regular voltmeter?
I think it doesn't draw any current from the source, so it's more accurate!
That’s a great observation! Let’s summarize our session: Current electricity plays a vital role in technology and understanding it is essential for future studies in physics.
Introduction & Overview
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Quick Overview
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Electric Current
Chapter 1 of 1
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Chapter Content
• Electric Current (I) is the rate of flow of electric charge through a conductor.
\[ I = \frac{Q}{t} \]
where \( I \) is the current, \( Q \) is the charge, and \( t \) is time.
• SI Unit: Ampere (A)
• Direction: Conventional current flows from positive to negative terminal (opposite to electron flow).
Detailed Explanation
Electric current is a fundamental concept in electricity, representing the flow of electric charge. The formula \( I = \frac{Q}{t} \) expresses current (I) as the amount of charge (Q) passing through a point in a conductor per unit time (t). The standard unit of electric current is the Ampere (A). This reflects how much charge flows in a circuit - more charge flowing per second means a higher current. It's important to note that while current is defined to flow from positive to negative (the conventional direction), electrons actually move from negative to positive.
Examples & Analogies
Think of electric current like water flowing through a pipe. Just as water flow can be measured in liters per second, electric current is measured in Amperes. If you have a larger pipe (more charge flow), more water (current) can pass through it in the same amount of time. Just like water flows from a higher pressure area to a lower pressure area, electric current flows from a positively charged area to a negatively charged area.
Key Concepts
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Electric Current: The flow of electrical charge, measured in Amperes.
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Ohm's Law: Describes the relationship between voltage, current, and resistance in conductors.
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Resistance: A measure of the opposition to current flow in a circuit.
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Resistivity: Indicates how strongly a material opposes current flow.
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Temperature Dependence: Resistance varies with temperature, increasing in conductors and decreasing in semiconductors.
Examples & Applications
A flashlight functioning due to the flow of current through its electrical circuit.
Using a potentiometer to accurately measure the voltage of different batteries.
Memory Aids
Interactive tools to help you remember key concepts
Memory Tools
For every charge that flows, an Ampere shows.
Stories
Imagine a river (current) carrying leaves (charges), encountering rocks (resistance) that change its flow.
Memory Tools
Use VIR: V = I * R when calculating voltage, current, and resistance!
Acronyms
KCL and KVL
'Current's Calming Law
and Voltage's Valuable Loop.'
Flash Cards
Glossary
- Electric Current
The rate of flow of electric charge through a conductor, measured in Amperes.
- Ohm's Law
The principle that states the voltage across a conductor is directly proportional to the current flowing through it.
- Resistance
The opposition to the flow of current, denoted by R.
- Resistivity
A material's inherent resistance per unit length and area under defined conditions.
- Kirchhoff's Laws
Rules for analyzing electrical circuits, including the current law and voltage law.
Reference links
Supplementary resources to enhance your learning experience.