When a DC current passes through a long straight conductor a magnetising force, H and a static Magnetic Field, B is developed around it If the wire is then wound into a coil, the magnetic field is greatly intensified producing a static magnetic field around itself forming the shape of a bar magnet giving a distinct North and South pole.
The magnetic flux developed around the coil being proportional to the amount of current flowing in the coils windings as shown. If additional layers of wire are wound upon the same coil with the same current flowing through them, the static magnetic field strength would be increased.
Therefore, the magnetic field strength of a coil is determined by the ampere turns of the coil. With more turns of wire within the coil, the greater the strength of the static magnetic field around it.
But what if we reversed this idea by disconnecting the electrical current from the coil and instead of a hollow core we placed a bar magnet inside the core of the coil of wire. By moving this bar magnet “in” and “out” of the coil a current would be induced into the coil by the physical movement of the magnetic flux inside it.
Likewise, if we kept the bar magnet stationary and moved the coil back and forth within the magnetic field an electric current would be induced in the coil. Then by either moving the wire or changing the magnetic field we can induce a voltage and current within the coil and this process is known as Electromagnetic Induction and is the basic principle of operation of transformers, motors and generators.
Electromagnetic Induction was first discovered way back in the 1830’s by Michael Faraday. Faraday noticed that when he moved a permanent magnet in and out of a coil or a single loop of wire it induced an ElectroMotive Force or emf, in other words a Voltage, and therefore a current was produced.
So what Michael Faraday discovered was a way of producing an electrical current in a circuit by using only the force of a magnetic field and not batteries. This then lead to a very important law linking electricity with Magnetism, Faraday’s Law of Electromagnetic Induction.
When the magnet shown below is moved “towards” the coil, the pointer or needle of the Galvanometer, which is basically a very sensitive centre zero’ed moving-coil ammeter, will deflect away from its centre position in one direction only. When the magnet stops moving and is held stationary with regards to the coil the needle of the galvanometer returns back to zero as there is no physical movement of the magnetic field.
Likewise, when the magnet is moved “away” from the coil in the other direction, the needle of the galvanometer deflects in the opposite direction with regards to the first indicating a change in polarity. Then by moving the magnet back and forth towards the coil the needle of the galvanometer will deflect left or right, positive or negative, relative to the directional motion of the magnet.
Electromagnetic Induction by a Moving Magnet
Likewise, if the magnet is now held stationary and ONLY the coil is moved towards or away from the magnet the needle of the galvanometer will also deflect in either direction. Then the action of moving a coil or loop of wire through a magnetic field induces a voltage in the coil with the magnitude of this induced voltage being proportional to the speed or velocity of the movement.
Then we can see that the faster the movement of the magnetic field the greater will be the induced emf or voltage in the coil, so for Faraday’s law to hold true there must be “relative motion” or movement between the coil and the magnetic field and either the magnetic field, the coil or both can move.
Faraday’s Law of Induction
From the above description we can say that a relationship exists between an electrical voltage and a changing magnetic field to which Michael Faraday’s famous law of electromagnetic induction states: “that a voltage is induced in a circuit whenever relative motion exists between a conductor and a magnetic field and that the magnitude of this voltage is proportional to the rate of change of the flux”.
Electric motor, any of a class of devices that convert electrical energy to mechanical energy, usually by employing electromagnetic phenomena. Most electric motors develop their mechanical torque by the interaction of Conductors carrying current in a direction at right angles to a magnetic field. The various types of electric motor differ in the ways in which the conductors and the field are arranged and also in the control that can be exercised over mechanical output torque, speed, and position.
Principle of operation
The basic principle on which motors operate is Ampere’s law. This law states that a wire carrying an electric current produces a magnetic field around itself. Imagine that current is flowing through The presence of that current creates a magnetic field around the wire. Since the loop itself has become a magnet, one side of it will be attracted to the north (N) pole of the surrounding magnet and the other side will be attracted to the south (S) pole of the magnet. The loop will begin to rotate.
AC motors. What happens next depends on the kind of electric current used to run the motor, direct (DC) or alternating (AC) current. With AC current, the direction in which the current flows changes back and forth rapidly and at a regular rate.
In the United States, the rate of change is 60 times per second, or 60 hertz (the unit of frequency).
In an AC motor, then, the current flows first in one direction through the wire loop and then reverses itself about 1/60 second later. This change of direction means that the magnetic field produced around the loop also changes once every 1/60 second. At one instant, one part of the loop is attracted by the north pole of the magnet, and at the next instant, it is attracted by the south pole of the magnet.
But this shifting of the magnetic field is necessary to keep the motor operating. When the current is flowing in one direction, the right hand side of the coil might become the south pole of the loop magnet. It would be repelled by the south pole of the outside magnet and attracted by the north pole of the outside magnet. The wire loop would be twisted around until the right side of the loop had completed half a revolution and was next to the north pole of the outside magnet.
If nothing further happened, the loop would come to a stop, since two opposite magnetic poles—one from the outside magnet and one from the wire loop—would be adjacent to (located next to) each other. And unlike magnetic poles attract each other. But something further does happen. The current changes direction, and so does the magnetic field around the wire loop. The side of the loop that was previously attracted to the north pole is now attracted to the south pole, and vice versa. Therefore, the loop receives another “kick,” twisting it around on its axis in response to the new forces of magnetic attraction and repulsion.
Thus, as long as the current continues to change direction, the wire loop is forced to spin around on its axis. This spinning motion can be used to operate any one of the electrical appliances mentioned above.
Capacitor
A capacitor is a device for storing electrical energy. Capacitors are used in a wide variety of applications today. Engineers use large banks of capacitors, for example, to test the performance of an electrical circuit when struck by a bolt of lighting. The energy released by these large capacitors is similar to the lightning bolt. On another scale, a camera flash works by storing energy in a capacitor and then releasing it to cause a quick bright flash of Light. On the smallest scale, capacitors are used in computer systems. A charged capacitor represents the number 1 and an uncharged capacitor a 0 in the binary Number System used by computers.
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Electromagnetic induction is the production of an electric current in a conductor due to a changing magnetic field. This is the principle behind many electrical devices, including generators, motors, and transformers.
Faraday’s law of induction states that the magnitude of the induced electromotive force (EMF) is proportional to the rate of change of the magnetic flux through the conductor. The direction of the induced EMF is given by Lenz’s law, which states that the induced EMF always opposes the change that produces it.
Eddy currents are electric currents that flow in closed loops within a conductor when it is exposed to a changing magnetic field. Eddy currents can cause heating and can also be used to generate electricity.
Self-induction is the phenomenon of an electric current being induced in a conductor by a change in the current flowing through that conductor. The magnitude of the self-induced EMF is proportional to the rate of change of the current.
Mutual induction is the phenomenon of an electric current being induced in a conductor by a change in the current flowing through a nearby conductor. The magnitude of the mutual-induced EMF is proportional to the mutual inductance between the two conductors.
An electric motor is a device that converts electrical energy into mechanical energy. Electric motors are used in a wide variety of applications, including power tools, appliances, and vehicles.
There are two main types of electric motors: DC motors and AC motors. DC motors are powered by direct current, while AC motors are powered by alternating current.
DC motors are typically used in applications where speed control is important, such as in power tools and appliances. AC motors are typically used in applications where high starting torque is required, such as in vehicles.
There are several different types of AC motors, including synchronous motors, induction motors, and stepper motors. Synchronous motors operate at a constant speed, regardless of the load. Induction motors are the most common type of AC motor. They are relatively inexpensive and easy to maintain. Stepper motors are used in applications where precise positioning is required, such as in computer printers and CNC machines.
Brushless DC motors are a type of DC motor that does not have brushes. Brushes are used to conduct electricity to the rotor of a DC motor. Brushless DC motors are more efficient than brushed DC motors and have a longer lifespan.
Switched reluctance motors are a type of AC motor that does not have permanent magnets. Switched reluctance motors are more efficient than induction motors and have a longer lifespan.
Permanent magnet synchronous motors are a type of AC motor that has permanent magnets on the rotor. Permanent magnet synchronous motors are more efficient than induction motors and have a longer lifespan.
Linear motors are a type of electric motor that produces linear motion, rather than rotary motion. Linear motors are used in a variety of applications, including maglev trains and 3D printers.
Electromagnetic induction is a fundamental principle of physics that has many important applications in technology. Electric motors are one of the most important applications of electromagnetic induction. Electric motors are used in a wide variety of applications, including power tools, appliances, and vehicles.
What is a Generator?
A generator is a device that converts mechanical energy into electrical energy. It does this by using a magnetic field to induce an electric current in a conductor.
How does a generator work?
A generator works by using a magnetic field to induce an electric current in a conductor. The magnetic field is created by a coil of wire that is wrapped around a Metal core. When the coil of wire is rotated, it cuts through the magnetic field, which induces an electric current in the wire.
What are the different types of generators?
There are two main types of generators: AC generators and DC generators. AC generators produce alternating current, which is the type of current that is used in most homes and businesses. DC generators produce direct current, which is the type of current that is used in batteries and other electronic devices.
What are the advantages and disadvantages of generators?
The advantages of generators include the fact that they are portable, reliable, and efficient. The disadvantages of generators include the fact that they can be noisy and expensive.
What are some common applications for generators?
Generators are used in a variety of applications, including:
- Powering homes and businesses during a power outage
- Providing backup power for critical systems
- Charging batteries
- Generating electricity for remote locations
What are some safety considerations when using generators?
When using generators, it is important to take the following safety precautions:
- Never operate a generator in an enclosed space.
- Make sure the generator is properly grounded.
- Keep children and pets away from the generator.
- Do not overload the generator.
- Use the correct type of fuel for the generator.
- Follow the manufacturer’s instructions.
What is a motor?
A motor is a device that converts electrical energy into mechanical energy. It does this by using a magnetic field to create a force that turns a shaft.
How does a motor work?
A motor works by using a magnetic field to create a force that turns a shaft. The magnetic field is created by a coil of wire that is wrapped around a metal core. When an electric current is passed through the coil of wire, it creates a magnetic field. This magnetic field interacts with the magnetic field of a permanent magnet, which creates a force that turns the shaft.
What are the different types of motors?
There are many different types of motors, but the most common types are:
- AC motors: AC motors use alternating current to create a magnetic field.
- DC motors: DC motors use direct current to create a magnetic field.
- Stepper motors: Stepper motors move in discrete steps, which makes them ideal for applications where precise positioning is required.
- Servo motors: Servo motors are used in applications where precise control of speed and position is required.
What are the advantages and disadvantages of motors?
The advantages of motors include the fact that they are efficient, reliable, and versatile. The disadvantages of motors include the fact that they can be noisy and expensive.
What are some common applications for motors?
Motors are used in a variety of applications, including:
- Powering appliances
- Operating machinery
- Driving vehicles
- Generating electricity
What are some safety considerations when using motors?
When using motors, it is important to take the following safety precautions:
- Make sure the motor is properly grounded.
- Keep children and pets away from the motor.
- Do not overload the motor.
- Use the correct type of motor for the application.
- Follow the manufacturer’s instructions.
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A coil of wire is placed in a magnetic field. If the magnetic field is increased, what will happen to the current in the coil?
(A) The current will increase.
(B) The current will decrease.
(C) The current will stay the same. -
A current is flowing through a coil of wire. If a magnet is placed near the coil, what will happen to the magnetic field of the coil?
(A) The magnetic field of the coil will increase.
(B) The magnetic field of the coil will decrease.
(C) The magnetic field of the coil will stay the same. -
A generator is a device that converts mechanical energy into electrical energy. How does a generator work?
(A) A generator uses a magnetic field to induce a current in a coil of wire.
(B) A generator uses a current to create a magnetic field.
(C) A generator uses a rotating coil of wire to create a magnetic field. -
An electric motor is a device that converts electrical energy into mechanical energy. How does an electric motor work?
(A) An electric motor uses a magnetic field to induce a current in a coil of wire.
(B) An electric motor uses a current to create a magnetic field.
(C) An electric motor uses a rotating coil of wire to create a magnetic field. -
What is the difference between an electric motor and a generator?
(A) An electric motor converts electrical energy into mechanical energy, while a generator converts mechanical energy into electrical energy.
(B) An electric motor uses a rotating coil of wire to create a magnetic field, while a generator uses a magnetic field to induce a current in a coil of wire.
(C) An electric motor has a permanent magnet, while a generator does not. -
What is the principle of electromagnetic induction?
(A) When a conductor is moved through a magnetic field, an electric current is induced in the conductor.
(B) When a magnetic field is changed, an electric current is induced in a conductor.
(C) When a conductor is placed in a magnetic field, an electric current is induced in the conductor. -
What is the difference between direct current (DC) and alternating current (AC)?
(A) DC is a type of current that flows in one direction, while AC is a type of current that flows in both directions.
(B) DC is a type of current that has a high voltage, while AC is a type of current that has a low voltage.
(C) DC is a type of current that is used in batteries, while AC is a type of current that is used in power lines. -
What is the purpose of a transformer?
(A) A transformer is used to increase or decrease the voltage of an alternating current.
(B) A transformer is used to convert direct current into alternating current.
(C) A transformer is used to convert alternating current into direct current. -
What is the difference between a step-up transformer and a step-down transformer?
(A) A step-up transformer increases the voltage of an alternating current, while a step-down transformer decreases the voltage of an alternating current.
(B) A step-up transformer is used to transmit electricity over long distances, while a step-down transformer is used to distribute electricity to homes and businesses.
(C) A step-up transformer has more turns on the secondary coil than the primary coil, while a step-down transformer has fewer turns on the secondary coil than the primary coil. -
What is the purpose of a rectifier?
(A) A rectifier is used to convert alternating current into direct current.
(B) A rectifier is used to convert direct current into alternating current.
(C) A rectifier is used to increase or decrease the voltage of an alternating current.