Ohms Law Explained | Practice Problems
Summary
TLDRIn this educational video, Professor Mad explains Ohm's Law, a fundamental concept in electronics. The script clarifies the behavior of electrons, the concept of voltage as electron pressure difference, and current as the flow of electrons. It also discusses resistance as the opposition to electron flow due to collisions. Ohm's Law is introduced, illustrating the direct relationship between current and voltage, and the inverse relationship with resistance. Practical examples demonstrate how to apply Ohm's Law to calculate voltage, current, and resistance in various circuits.
Takeaways
- đ Ohm's Law is a fundamental concept in electronics, describing the relationship between voltage, current, and resistance.
- đ« Electrons repel each other and prefer to move from high electron pressure to low electron pressure, which is analogous to water flowing from high to low ground.
- ⥠Voltage is the electron pressure difference that motivates electrons to move and is measured in volts.
- đ Electrons move from the negative to the positive side, but the current is conventionally said to flow in the opposite direction.
- đ Current represents the flow of electrons and is measured in amperes, with the direction typically opposite to the actual electron flow.
- đĄ Resistance is the opposition to electron flow caused by collisions with atoms in the material, measured in ohms.
- đ Conductive materials with fewer obstacles for electrons are considered low resistance, allowing for faster electron movement.
- đ§ Materials with many obstacles for electrons are high resistance, slowing down the electron movement.
- âïž Ohm's Law states that the current through a circuit is directly proportional to the voltage and inversely proportional to the resistance.
- đ Ohm's Law can be rearranged into three forms: resistance equals voltage divided by current, voltage equals current times resistance, and current equals voltage divided by resistance.
- đ Problem-solving with Ohm's Law involves calculating unknown quantities such as voltage, current, or resistance given the other two, using the formulas derived from Ohm's Law.
Q & A
What is Ohm's law and why is it fundamental in electronics?
-Ohm's law is a principle that describes the relationship between voltage, current, and resistance in an electrical circuit. It is fundamental because it provides the basic equation that relates these three quantities, allowing us to calculate any one of them if the other two are known.
Why do electrons always try to move away from each other?
-Electrons are negatively charged particles, and they repel each other due to their like charges. This repulsion causes them to move away from each other, creating a pressure that can be relieved by providing a path for the electrons to move to an area with fewer electrons.
What is the difference between electron flow and current direction as described in the script?
-Electrons, being negatively charged, naturally flow from the negative side to the positive side. However, by convention, the direction of electric current is considered to be the opposite, from the positive side to the negative side. This is because historically, the direction of current was defined before the charge of electrons was understood.
How is voltage related to the movement of electrons?
-Voltage, or electric potential difference, is the driving force that causes electrons to move from one point to another. It represents the electron pressure difference between two points and is measured in volts.
What is resistance and how does it affect the flow of electrons?
-Resistance is the opposition that a material offers to the flow of electrons, caused by collisions of electrons with atoms within the material. It slows down the movement of electrons and is measured in ohms. Materials with fewer obstacles (atoms) for the electrons to collide with are called low resistance, while those with more obstacles are high resistance.
How does Ohm's law express the relationship between current, voltage, and resistance?
-Ohm's law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. Mathematically, it is expressed as I = V/R.
What happens to the current when the voltage in a circuit is increased?
-When the voltage in a circuit is increased, the electrons move faster, resulting in a higher current. Conversely, if the voltage is decreased, the electrons move slower, leading to a lower current.
How does increasing resistance affect the current in a circuit?
-If the resistance in a circuit is increased, the electrons face more collisions, which slows down their movement and thus lowers the current. If the resistance is decreased, the electrons face fewer collisions, speeding up their movement and increasing the current.
What are the three forms of Ohm's law mentioned in the script?
-The three forms of Ohm's law are: 1) Current (I) equals Voltage (V) divided by Resistance (R), 2) Resistance (R) equals Voltage (V) divided by Current (I), and 3) Voltage (V) equals Current (I) times Resistance (R).
Can you provide an example of how to calculate the voltage across a resistor using Ohm's law?
-Sure. If a resistor has a resistance of 25 ohms and a current of 0.25 ampere flows through it, the voltage across the resistor can be calculated using Ohm's law: V = I * R, which gives V = 0.25 * 25 = 6.25 volts.
How can you calculate the current flowing through a light bulb with a known resistance and voltage?
-Using Ohm's law, if a light bulb has a resistance of 240 ohms and is connected to a 120-volt power source, the current flowing through it can be calculated as I = V/R, which gives I = 120/240 = 0.5 ampere.
What is the resistance of a hairdryer that operates at 220 volts and draws a current of 5 amperes?
-Using Ohm's law, the resistance (R) of the hairdryer can be calculated as R = V/I, which gives R = 220/5 = 44 ohms.
Outlines
đ Ohm's Law and Basic Electronics Concepts
This paragraph introduces Ohm's Law, a fundamental principle in electronics. It discusses the behavior of electrons, their repulsion from each other, and how they move from areas of high electron pressure to low pressure through a conductor when a potential difference, or voltage, is applied. The paragraph clarifies the direction of electron flow versus conventional current flow, emphasizing that electrons move from the negative to the positive side, but the current is described as flowing in the opposite direction. It introduces the concept of resistance, which is the opposition to electron flow caused by collisions with atoms in the material. The paragraph concludes by defining the three key elements of electronics: voltage, current, and resistance, and Ohm's Law, which describes their interrelationship.
đ§ Applying Ohm's Law to Circuits and Problem Solving
The second paragraph delves into the practical application of Ohm's Law in electrical circuits. It explains how a battery provides voltage for electron flow and the role of internal resistance in a light bulb. The paragraph illustrates the inverse relationship between current and resistance, showing that an increase in resistance leads to a decrease in current, and vice versa. It then provides step-by-step examples of how to use Ohm's Law to calculate voltage, current, and resistance in different scenarios, such as calculating the voltage across a resistor given its resistance and the current flowing through it, determining the current through a light bulb with known resistance and voltage, and finding the resistance of a hairdryer given its operating voltage and the current it draws. The paragraph concludes with an invitation to join the creator's Patreon community and to follow for more educational content.
Mindmap
Keywords
đĄElectrons
đĄElectron Pressure
đĄVoltage
đĄCurrent
đĄResistance
đĄOhm's Law
đĄConductor
đĄDirect Proportionality
đĄInverse Proportionality
đĄCircuit
đĄProblem Solving
Highlights
Ohm's law is one of the most fundamental and important concepts in electronics.
Electrons always try to move away from each other, creating electron pressure.
Electrons move from high to low electron pressure, which is facilitated by a conductor.
Voltage is the electron pressure difference, motivating electrons to move from one point to another.
Electrons are negatively charged and move from the negative side to the positive side.
Electric current is the flow of electric charge, technically a negative flow but called positive in common terms.
Resistance is the opposition to electron flow caused by collisions with atoms in a material.
Materials with fewer obstacles for electrons are considered low resistance, allowing faster electron movement.
High resistance materials have more obstacles, slowing down electron movement.
Ohm's law states the current is directly proportional to voltage and inversely proportional to resistance.
Voltage, current, and resistance are the three basic pillars of electronics.
Voltage is measured in volts, current in amps, and resistance in ohms.
Ohm's law can be expressed in three forms: I=V/R, R=V/I, and V=IR.
The battery supplies the voltage for electrons to flow in a circuit.
The light bulb's internal resistance opposes the current flow.
Using Ohm's law, the current is calculated as voltage divided by resistance.
Example problem: Calculating the voltage across a resistor with given resistance and current.
Example problem: Calculating the current flowing through a light bulb with given resistance and voltage.
Example problem: Calculating the resistance of a hairdryer with given voltage and current.
The importance of sketching a circuit to understand the problem better.
Invitation to join Patreon, like, and subscribe for more content from Professor Mad.
Transcripts
welcome to Professor mad in this video
we're going to talk about Oh's law one
of the most fundamental and important
Concepts in the world of electronics
let's start with
electrons one of the most fundamental
properties of electrons is that they
don't like each other they always try to
move away from each other as much as
possible when a lot of electrons are
crammed into one place a huge tension or
pressure builds up imagine a crowded
room where nobody wants to be near each
other it gets pretty
intense if we provide an Escape Route
for these electrons to move to an area
with fewer electrons they'll eagerly
move
along it's like rolling balls from High
Ground to low
ground electrons always prefer to move
from high electron pressure to low
pressure so to move electrons from one
place to another we need to connect two
areas with conductor where there is a
difference in electron
pressure this electron pressure
difference is known as
voltage since electrons are negatively
charged we label the high press side
with a negative symbol and the low
pressure side with a positive symbol
therefore electrons move from the
negative side to the positive
side the movement of electrons creates a
flow of electric charge which we term as
electric current since electrons are
negatively charged this flow is
technically a negative current but we
humans prefer positive things so when
there's a negative current flowing in
One Direction we call it a positive
current flowing in the opposite
direction in fact almost every time we
use the term current we're actually
referring to the direction opposite to
the electron flow so while electrons
always flow from the negative side to
the positive side the current is said to
flow from the positive side to the
negative side it might seem a bit
confusing but that's just how we roll in
the world of
electronics now we know two things about
Electronics voltage and current there is
one more important factor to consider
resistance even though conductive
materials allow electrons to move
through them it doesn't mean that
electrons go straight from the negative
side to the positive side there are
trillions of atoms between the two ends
of a
conductor as electrons try to move to
the positive side they collide with
these atoms causing their path to
deviate so resistance is the opposition
of material shows to electron flow
caused by collisions of electrons with
obstacles if the path has fewer
obstacles the electrons will move
quickly from negative side to positive
side we call these materials low
resistance however if there are many
obstacles the movement of electrons
slows down and we call these materials
High
Resistance so these collisions are what
actually cause resistance
now we know the three basic pillars of
electronics voltage the electron
pressure difference that motivates
electrons to move from one point to
another we measure voltage using the
unit
volts current the flow of electrons
moving from high electron pressure to
low electron pressure we measure the
amount of electron flow per second using
the unit amps
resistance the opposition of material
shows to electron flow caused by
collisions of electrons with obstacles
resistance is measured using the unit
ohms ohms law describes the relationship
among these three quantities in simple
terms Ohm's law says the current through
a circuit is directly proportional to
the voltage and inversely proportional
to the resistance let's illustrate this
the current is directly proportional to
the voltage
here the voltage is increasing from V1
to
V3 let's see what happens to the
current it's clear the current is also
increasing from i1 to I3 if we increase
the voltage electrons move faster
resulting in a higher current if we
decrease the voltage electrons move
slower resulting in a lower current now
let's illustrate what happens to the
current with different resistances the
current is inversely proportional to the
resistance here the resistance is
increasing from R1 to R3 let's see what
happens to the
current it's clear the current is
decreasing from i1 to
I3 if we increase the resistance
electrons face more collisions slowing
down their movement which lowers the
current if we decrease the resistance
electrons face fewer collisions speed in
up their movement which increases the
current let's apply this knowledge to a
circuit the battery supplies the
required voltage for electrons to flow
the electrons flow from the negative
side to the positive side but we say the
current flows from positive to
negative the light bulb has internal
resistance that opposes the
current according to M's law the current
through a circuit is directly
proportional to the voltage and
inversely proportional to the
resistance by combining these
relationships we get that the current is
equal to the voltage divided by the
resistance we can arrange this
relationship in three forms resistance
is equal to the voltage divided by the
current voltage is equal to the current
times the resistance you should be able
to use all three forms appropriately
depending on the problem you're
solving now let's solve some problems
using ohms law calculate the voltage
across this resistor we can see the
resistance of the resistor is 25 Ohms a
current of 250 milliamp goes through the
circuit which we can write as 0.25 amp
so what is the voltage let's use Ohm's
law voltage equals the current times the
resistance so let's substitute the
values by solving we get the voltage the
voltage across the resistor is 6.25
volts let's move on to the next question
question if a light bulb has a
resistance of 240 ohms and is connected
to a 120 volt power source calculate the
current flowing through
it first sketch the circuit this will
help you understand the problem
better now the resistance is 240 ohms
and the voltage is 120 volts we have to
calculate the
current let's use Ohm's law current is
equal to the voltage divided by the
resistance
so let's substitute the values by
solving we get the current so the
current flowing through the light bulb
is 0.5
amp let's discuss one last problem if a
hairdryer operates at 220 volts and
draws a current of 5 amp calculate its
resistance first sketch the circuit this
will help you understand the problem
better now the current is 5 amps and the
voltage is 220 volts we have to
calculate the
resistance let's use Ohm's law
resistance is equal to the voltage
divided by the current so let's
substitute the values by solving we get
the resistance so the resistance of this
hair dryer is 44
ohms that's all for today if you think
my contents are valuable to the world
you are welcome to join my patreon
community
like And subscribe to Professor mad for
more interesting videos
Voir Plus de Vidéos Connexes
Resistors | Electricity | Physics | FuseSchool
Electric Current & Circuits Explained, Ohm's Law, Charge, Power, Physics Problems, Basic Electricity
Ohmâs Law Tutorial with easy practice problems | Basic Circuits
Electric Current: Crash Course Physics #28
Introduction to circuits and Ohm's law | Circuits | Physics | Khan Academy
Basic Electricity - Resistance and Ohm's law
5.0 / 5 (0 votes)