When we pass an electrical current through a wire, it creates a magnetic field around the wire. If we change the direction of the current, the magnetic field also changes direction. This can be observed by placing compasses around the wire. When an AC (alternating current) generator is connected to a closed loop of wire, the magnetic field inside the generator pushes and pulls the electrons in the wire. This causes them to move back and forth, constantly changing direction. As a result, the magnetic field keeps reversing, and the voltage fluctuates between maximum and minimum values, forming a sine wave pattern.
If we connect an oscilloscope to a power outlet, we can see this pattern repeating 50 or 60 times per second, depending on whether it’s a 50 or 60 hertz supply. In North America, the AC frequency is 60 hertz, while most of the world uses 50 hertz. With a transformer, the frequency we input is the frequency we get out; we can only change the voltage, not the frequency.
When we wrap the wire into a coil, the magnetic field becomes stronger. The wire must be insulated with an enamel coating to ensure the current flows along the entire length; otherwise, it will take the shortest route and not function properly. If we place a second coil or wire close to the first coil, the magnetic field will induce a voltage in the second coil, pushing and pulling the electrons and causing them to move. This is how a transformer operates.
The same principle applies if we move a magnet past a coil of wire; the magnet will induce a voltage in the coil. The key component here is that the magnetic field is constantly changing in polarity and intensity, which disturbs the free electrons and causes them to move, a phenomenon we call electromotive force. However, this only works with alternating current. If we connect a direct current supply to the transformer, the flow of electrons will create a magnetic field around the primary coil, but this will be constant and fixed in polarity and intensity, so it will not disturb the electrons in the secondary side. The only time it will create an electromotive force using direct current is briefly when the switch is opened and closed, as this energizes and de-energizes the magnetic field of the coil.
Notice that when a DC current passes through a transformer, we get a brief voltage spike as the magnetic field increases and decreases. In contrast, with an AC supply, we get a constant output voltage because the magnetic field is constantly changing. This is why we use alternating current.
We can use two separate coils of wire as a transformer, but it won’t be very efficient. The problem is that we waste a lot of the magnetic field because it’s not within range of the secondary coil. To improve efficiency, we place a ferromagnetic iron core between the coils, which concentrates the magnetic field and guides it to the secondary coil. However, this is not a perfect solution, as it can result in eddy currents flowing around the core, which heats up the transformer and wastes energy.
To reduce this, the core is made of many thin laminated sheets, which restrict the movement of eddy currents and minimize their effects. Although we still lose some magnetic field due to leakage flux and experience losses at the joints, we also lose energy in the wire and coils due to resistance, which generates heat. In a transformer, we have copper losses as well as iron losses. The alternating current causes the sheets to expand and contract slightly, creating vibrations between the sheets, which is why we hear a humming sound.
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Create a basic transformer using insulated wire and a small iron core. Wrap two separate coils around the core and connect one to a small AC power source. Observe how the voltage changes in the second coil using a multimeter. This hands-on activity will help you understand how transformers work and the role of coils and cores in voltage transformation.
Use an oscilloscope to visualize the sine wave pattern of AC voltage. Connect it to a power outlet and observe the waveform. Try changing the frequency settings to see how the waveform changes. This activity will help you understand AC frequency and its significance in electrical systems.
Use a compass to map the magnetic field around a current-carrying wire. Change the direction of the current and observe how the compass needle responds. This will help you visualize the relationship between electric current and magnetic fields, reinforcing the concept of electromotive force.
Experiment with different core materials and coil configurations to see how they affect transformer efficiency. Measure the output voltage and heat generated in each setup. This will give you insights into core design and the factors affecting transformer efficiency.
Research the applications of transformers in everyday life and present your findings to the class. Focus on how transformers are used in power distribution, electronics, and renewable energy systems. This will help you appreciate the practical importance of transformers in modern technology.
Here’s a sanitized version of the provided YouTube transcript:
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When we pass an electrical current through a wire, it generates a magnetic field around the wire. If we reverse the direction of the current, the magnetic field also reverses. We can observe this by placing compasses around the wire. When we connect an AC generator to a closed loop of wire, the magnetic field inside the generator pushes and pulls the electrons in the wire, causing them to constantly alternate direction between moving forwards and backwards. As a result, the magnetic field is constantly reversing, and the voltage varies between maximum and minimum values, which is why we see a sine wave pattern.
If we connect an oscilloscope to a power outlet, this pattern repeats 50 or 60 times per second, depending on whether it’s a 50 or 60 hertz supply. The AC frequency in North America is 60 hertz, while most of the world uses 50 hertz. With a transformer, the frequency we input is the frequency we get out; we can only increase or decrease the voltage, not the frequency.
When we wrap the wire into a coil, the magnetic field becomes even stronger. The wire must be insulated with an enamel coating to ensure the current flows along the entire length; otherwise, it will take the shortest route and not function properly. If we place a second coil or wire close to the first coil, the magnetic field will induce a voltage in the second coil, pushing and pulling the electrons and causing them to move. This is how a transformer operates.
The same principle applies if we move a magnet past a coil of wire; the magnet will induce a voltage in the coil. The key component here is that the magnetic field is constantly changing in polarity and intensity, which disturbs the free electrons and causes them to move, a phenomenon we call electromotive force. However, this only works with alternating current. If we connect a direct current supply to the transformer, the flow of electrons will create a magnetic field around the primary coil, but this will be constant and fixed in polarity and intensity, so it will not disturb the electrons in the secondary side. The only time it will create an electromotive force using direct current is briefly when the switch is opened and closed, as this energizes and de-energizes the magnetic field of the coil.
Notice that when I pass a DC current through this transformer, we get a brief voltage spike as the magnetic field increases and decreases. In contrast, with an AC supply, we get a constant output voltage because the magnetic field is constantly changing. This is why we use alternating current.
We can use two separate coils of wire as a transformer, but it won’t be very efficient. The problem is that we waste a lot of the magnetic field because it’s not within range of the secondary coil. To improve efficiency, we place a ferromagnetic iron core between the coils, which concentrates the magnetic field and guides it to the secondary coil. However, this is not a perfect solution, as it can result in eddy currents flowing around the core, which heats up the transformer and wastes energy.
To reduce this, the core is made of many thin laminated sheets, which restrict the movement of eddy currents and minimize their effects. Although we still lose some magnetic field due to leakage flux and experience losses at the joints, we also lose energy in the wire and coils due to resistance, which generates heat. In a transformer, we have copper losses as well as iron losses. The alternating current causes the sheets to expand and contract slightly, creating vibrations between the sheets, which is why we hear a humming sound.
Check out one of these videos to continue learning about electrical engineering, and I’ll catch you in the next lesson. Don’t forget to follow us on social media for more updates!
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This version maintains the technical content while removing any informal language or unnecessary details.
Transformer – A device that transfers electrical energy between two or more circuits through electromagnetic induction. – The transformer in the power station steps up the voltage for efficient transmission over long distances.
Magnetic – Relating to or exhibiting magnetism, the force exerted by magnets when they attract or repel each other. – The magnetic field around a current-carrying wire can be visualized using iron filings.
Current – The flow of electric charge in a conductor, typically measured in amperes. – The electric current flowing through the circuit was measured to be 5 amperes.
Voltage – The electric potential difference between two points, which causes current to flow in a circuit. – The voltage across the battery terminals was measured to be 12 volts.
Coil – A series of loops that has been wound or gathered, often used in electrical applications to create magnetic fields. – The coil in the motor generates a magnetic field when current passes through it.
Frequency – The number of cycles per unit time of a periodic wave, typically measured in hertz (Hz). – The frequency of the alternating current in household outlets is usually 60 Hz.
Electromotive – Relating to the force that causes electrons to move, creating an electric current. – The electromotive force generated by the battery is responsible for driving the current through the circuit.
Efficiency – The ratio of useful output energy to the total input energy, often expressed as a percentage. – The efficiency of the solar panel was calculated to be 20%, meaning it converts 20% of the sunlight into electrical energy.
Energy – The capacity to do work, which can exist in various forms such as kinetic, potential, thermal, electrical, etc. – The energy stored in the capacitor is released when the circuit is closed.
Resistance – The opposition to the flow of electric current, resulting in the conversion of electrical energy into heat, measured in ohms. – The resistance of the wire increased as its temperature rose.
