transformers for IGCSE Physics, GCE O level Physics
Summary
TLDRThis script explores the concept of mutual induction in transformers, explaining how an electromagnet induces an EMF in a second solenoid. It delves into the workings of transformers, distinguishing between step-up and step-down types, and their crucial role in the National Grid to minimize energy loss through high voltage transmission. The script also highlights the inefficiency of transformers with DC and the importance of AC in power transmission, concluding with a demonstration of power loss calculations in cables at different voltages.
Takeaways
- 🧲 Mutual Induction: When an electromagnet is switched on or off, a momentary EMF is induced in a nearby solenoid due to the changing magnetic field.
- 🔧 Steady Current No EMF: A steady current through an electromagnet does not induce EMF in a secondary solenoid because the magnetic field remains constant.
- 🔄 Alternating Current Effect: Using an alternating power supply results in an alternating magnetic field that induces an alternating EMF in the secondary solenoid.
- 🔗 Increasing Induced EMF: The induced EMF in the secondary solenoid can be increased by adding more turns to the coil or using an iron core that extends through the secondary solenoid.
- 🌐 Principle of Transformers: Transformers operate on the principle of mutual inductance to transfer electrical energy efficiently between two coils.
- ⚙️ Components of a Transformer: A basic transformer consists of an AC input power supply, a primary coil, an iron core, and a secondary coil.
- ⏫⏬ Types of Transformers: There are step-up transformers that increase voltage and step-down transformers that decrease voltage, differentiated by the number of turns on their coils.
- 🔌 National Grid Application: Transformers are crucial in the National Grid for transmitting electricity at high voltages and low currents to minimize energy loss.
- ⚡ High Voltage Dangers: High voltage transmission requires safety measures such as elevated pylons or underground cables to avoid danger.
- 🔌 AC vs. DC in Transformers: Transformers work with AC currents, which can be easily stepped up or down, unlike DC which does not induce EMF due to its steady magnetic field.
- 📉 Power Loss Calculation: Demonstrates that high voltage transmission reduces power loss in cables, as shown by comparing power losses at different voltages and currents.
Q & A
What is the phenomenon of mutual induction?
-Mutual induction occurs when an electromotive force (EMF) is induced in a secondary solenoid due to the changing magnetic field created by a current in a nearby primary solenoid.
Why is there no EMF induced in the second solenoid with a steady current through the electromagnet?
-No EMF is induced in the second solenoid with a steady current because the magnetic field is not changing; mutual induction requires a varying magnetic field.
What happens when an alternating power supply is used instead of a DC power supply in an electromagnet?
-An alternating power supply creates an alternating magnetic field around the electromagnet, which interacts with the secondary solenoid, inducing an alternating EMF in it.
How can the induced EMF in the second solenoid be increased?
-The induced EMF in the second solenoid can be increased by increasing the number of turns on the secondary solenoid, using an iron core in the electromagnet, or having the iron core go right through the secondary solenoid.
What is a transformer and what is its primary function?
-A transformer is an electrical device used to increase or decrease the voltage of an AC current. It works based on the principle of mutual induction between two coils.
Why are transformers not effective with DC power?
-Transformers are not effective with DC power because DC creates a steady magnetic field that does not interact with the coil to induce an EMF.
What are the two main types of transformers?
-The two main types of transformers are step-up transformers, which increase the voltage of an input power supply, and step-down transformers, which decrease the voltage.
How do transformers help reduce energy loss in the National Grid?
-Transformers help reduce energy loss by allowing electricity to be transmitted at high voltages and low currents, which minimizes the amount of energy lost as heat in the transmission lines.
What is the significance of using high voltage transmission lines for long-distance electricity transmission?
-High voltage transmission lines are used to minimize energy loss during long-distance transmission. By increasing the voltage and reducing the current, thinner, lighter, and cheaper cables can be used.
Why is alternating current preferred for electricity transmission over long distances?
-Alternating current is preferred for long-distance transmission because it can be easily stepped up and down in voltage using transformers, which helps in minimizing power loss and efficiently transmitting electricity.
How does the power loss in a cable relate to the current flowing through it?
-The power loss in a cable is directly proportional to the square of the current flowing through it (as per the formula Power Loss = Current^2 * Resistance). Therefore, reducing the current for the same power transmission reduces the power loss.
Outlines
🌐 Principles of Electromagnetism and Transformers
This paragraph explains the fundamental principles of electromagnetism, specifically mutual induction, which is the process by which an electromagnet induces an electromotive force (EMF) in a nearby solenoid. It describes how a steady current does not induce an EMF, but a changing magnetic field does. The concept of transformers is introduced, which are devices that use mutual induction to either increase or decrease the voltage of an alternating current (AC). The paragraph also details the components of a transformer, the types of transformers (step-up and step-down), and their function in electrical grids to transmit electricity efficiently with minimal energy loss. The importance of using iron cores and the inability of transformers to work with direct current (DC) due to the lack of a changing magnetic field is also highlighted.
🔌 High Voltage Transmission and Energy Efficiency
The second paragraph delves into the practical application of transformers in high voltage transmission systems like the National Grid. It illustrates how step-up transformers reduce current and increase voltage, making it safer and more efficient to transmit electricity over long distances. The paragraph provides an example of how a power station's output is transformed to minimize energy loss due to heat in transmission lines. It also explains the use of step-down transformers to adjust voltage levels for safe use in urban areas and homes. The importance of alternating current (AC) in this process is emphasized, as it allows for easy voltage transformation, unlike direct current (DC). The paragraph concludes with a comparison of power loss in cables at different voltages, demonstrating the energy efficiency of high voltage transmission.
Mindmap
Keywords
💡Mutual Induction
💡Electromagnet
💡EMF (Electromotive Force)
💡Alternating Current (AC)
💡Transformer
💡Step-up Transformer
💡Step-down Transformer
💡National Grid
💡High Voltage Transmission
💡Power Loss
💡Iron Core
Highlights
Candidates are expected to have a thorough understanding of the syllabus and details outlined in the accompanying figure.
Mutual induction occurs when an electromagnet is switched on, inducing an EMF in the second solenoid for a momentary pulse.
A steady current through the electromagnet does not induce EMF in the second solenoid, as the magnetic field is not changing.
When the electromagnet is switched off, an EMF is induced in the opposite direction in the second solenoid for a momentary pulse, equivalent to pulling a magnet away quickly.
An alternating power supply creates an alternating magnetic field, inducing an alternating EMF in the second solenoid.
The induced EMF in the second solenoid can be increased by increasing the number of turns on the secondary coil.
Using an iron core in the electromagnet that goes through the secondary solenoid enhances mutual inductance.
Transformers apply the principle of mutual inductance to efficiently transfer electrical energy between two coils.
A transformer has four main components: AC input power supply, primary coil, iron core, and secondary coil.
Iron is used in transformers because it is a soft magnetic material that is easily magnetized and demagnetized.
Transformers will not work with DC as it creates a steady magnetic field that does not induce EMF in the coil.
There are two types of transformers: step-up and step-down, which increase or decrease the voltage of an input power supply respectively.
The voltage and current in a transformer are related by the ratio of turns on the primary and secondary coils.
Transformers help reduce energy loss in transmission by allowing electricity to be transmitted at high voltages and low currents.
National Grids use transformers to minimize heat loss by transmitting electricity at high voltages and decreasing it for household use.
High voltage transmission lines are used to minimize power loss over long distances by reducing the current.
AC is used for transmission because it can be easily stepped up and down in voltage using transformers, unlike DC.
Calculations demonstrate that less power is lost from a cable when power is transmitted at high voltage.
The video aims to be helpful and encourages viewers to subscribe, share, like, and leave positive comments for support.
Transcripts
[Music]
candidates are expected to have a
thorough understanding of the syllabus
details outlined in the accompanying
figure Mutual
induction as the electromagnet is
switched on an EMF is induced in the
second solenoid but only for a momentary
pulse this effect is equivalent to
pushing a magnet toward the second
solenoid very fast with a steady current
through the electric no EMF is induced
in the second solenoid because the
magnetic field is not changing as the
electromagnet is Switched Off an EMF is
induced in the opposite direction in the
second solenoid but only for a momentary
pulse this effect is equivalent to
pulling a magnet away from the second
solenoid very fast when an alternating
power supply is used instead of the DC
power supply an alternating current
flows through an electromagnet creating
an alternating magnetic field around it
this alternating magnetic field
interacts with second solenoid inducing
an alternating EMF in it the induced EMF
in the second solenoid can be increased
by increasing the number of turns on the
secondary Sol solenoid using an iron
core in the electromagnet that goes
right through the secondary
solenoid this principle is applied in
Transformers where the mutual inductance
between two coils allows for the
efficient transfer of electrical energy
between
them a simple
Transformer a Transformer is an
electrical device that can be used to
increase or decrease the voltage of an
AC current it works by Mutual
induction it has four main
components the AC input power
supply primary coil iron core and
secondary coil iron is used because it
is soft magnetic material that is easily
magnetized and
demagnetized when an alternating current
flows through the primary coil creating
and changing magnetic field around it
the iron core is easily magnetized so
the changing magnetic field passes
through it to the secondary coil this
changing magnetic field interacts with
the secondary coil inducing an
alternating voltage or EMF in the
secondary coil that has same frequency
as the input alternating
voltage if the secondary coil is part of
a complete circuit it will cause an
alternating current to flow Transformers
will not work with DC because it creates
a steady magnetic field that does not
interact with the coil and induce an
EMF there are two types of Transformers
as the step up and step down
Transformers Step up
Transformer it increases the voltage of
an input power supply meaning VP is less
than VSS and the number of turns on the
primary coil is less than the number of
turns on the secondary coil Step Down
Transformer it decreases the voltage of
an input power supply meaning V
is more than vs and the number of turns
on the primary coil is more than the
number of turns on the secondary coil
assuming all magnetic field lines pass
through both coils and there is no
energy lost due to heating effects the
following equations apply where VP is
the voltage in the primary coil vs is
the voltage in the secondary coil NP is
the number of turns on the primary coil
NS is the the number of turns on the
secondary coil the output power will be
the same as the input power of Supply
where VP is the voltage in the primary
coil IP is the current in the primary
coil VSS is the voltage in the secondary
coil is is the current in the secondary
coil National Grid are networks of wires
and cables that carry electrical energy
from Power stations to consumers such
factories and
homes however currents in Long wires can
lose lots of energy in the form of heat
the larger the current the greater the
amount of energy lost if the current in
the wires is kept to a minimum the heat
losses can be
reduced Transformers help us do this
Transformers are used in National Grids
so that the electricity is transmitted
as low currents and as at high
voltages typically a large Power Station
produces a current of 20,000 amp at a
voltage of 33,000 volts the high current
is fed to a step-up Transformer which
greatly decreases the size of the
currents and increase the size of the
voltages these stepup Transformers
increase the voltage of the electricity
to approximately 400,000 volts high
voltages like these can be extremely
dangerous so the cables are supported
high above the ground on
pylons as the cables enter town and
cities they are buried
underground close to where the
electrical energy is needed the
electricity is sent through a Step Down
Transformer that decreases the voltage
to approximately 230 volts while at the
same time increasing the
current high voltage
transmission when electricity is
transmitted over large distances the
current in the wires Heats them
resulting in energy loss to minimize
this loss we use high voltage
transmission lines by using a
Transformer to increase the voltage the
current is
reduced this means we can use thinner
lighter and cheaper cables to transmit
the same amount of power for example
aluminum cable alternating current is
used for the transmission because
alternating current can be easily
stepped up and down in voltage using
Transformers this means that
Transformers only work with AC
Transformers will not work with
DC the calculation demonstrates why less
power is lost from a cable if power is
transmitted through it at high
voltage the first circuit the power
input is 2,000 watt 200 volts and cable
resistance of 2 Ohms a current flows
through the cable can be calculated ated
by power equals current time voltage to
substitute the power is 2,000 and
voltage is 200 the results of current is
10
amp when a current flows through a
resistance it has a heating effect so
power is wasted the power loss can be
calculated by power equals current
squared times
resistance to substitute current is 10
and resistance is two
the results of power loss is 200 Watts
the second circuit increases in the
voltage from 200 to 2,000 volts while
the power and resistance of the cable
remain the same a current flows through
the cable reduces to 1 ampere the power
loss in the cable becomes 2 Watts these
calculations show the power losses in a
cable when the same amount of power is
sented high voltage is less than the low
voltage
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