1 . To study the magnetic field of a Circular Coil carrying current.


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Practical Applications of To study the magnetic field of a Circular Coil carrying current.


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Index : 

1.Name of experiment 2.Ojective of experiment 3.Basic Understanding 4.Practical Applications. Index

Experiment 1 by Chunesh Bhalla : 

To study Magnetic field along the axis of a current carrying coil Experiment 1 by Chunesh Bhalla

Slide 3: 

Objective of experiment To understand the concept of electromagnetism. Our setup is helpful for study of magnetic field around the current carrying coil. The setup illustrates how magnetic field generates by applying electric current in any current carrying conductor.

Electromagnetism : 

A magnetic field is produced when an electric current flows through a coil of wire. This is the basis of the electromagnet. We can make an electromagnet stronger by doing these things: wrapping the coil around an iron core adding more turns to the coil increasing the current flowing through the coil. Electromagnetism

Slide 5: 

What produces electromagnetism in electrons Every electron by its nature, is a small magnet. Ordinarily, the Countless Electrons in a material are randomly oriented in different directions, leaving no effect on average, but in a bar magnet the electrons are aligned in the same direction, so they act cooperatively, creating a net magnetic field. In addition to the electron's intrinsic magnetic field, there is sometimes An Additional magnetic field that results from the electron's orbital Motion about the nucleus. This effect is analogous to how a current carrying loop of wire generates a magnetic field.

Oersted’s Experiment : 

Oersted’s Experiment

What Is a Permanent Magnet? : 

A piece of iron or steel which produces a magnetic field Two ends of the permanent magnet are usually designated North and South Opposite magnet ends attract and like magnet ends repel What Is an Electromagnet? What Is a Permanent Magnet? Electromagnets behave like permanent magnets; but their magnetic field is not permanent. Magnetic field is temporarily induced by an electric current

A Simple Electromagnet: : 

A Simple Electromagnet:

Slide 9: 

Magnetic Field And its Basics

Slide 10: 

Magnetic field pattern around a straight wire. The resulting magnetic field lines form concentric circles around the wire. The Right-Hand Grip rule can be used to predict the direction of the magnetic field

Magnetic field pattern around a flat coil : 

Magnetic field pattern around a flat coil A solenoid is obtained by increasing the number of turns of a flat coil. The resulting magnetic field pattern of a solenoid resembles that of a bar magnet.

Magnetic field pattern around a flat coil : 

Magnetic field pattern around a flat coil The magnetic field strength in a solenoid can be increased by: 1) increasing the current, 2) increasing the number of turns per unit length of the solenoid, or 3) placing a soft iron core within the solenoid. The soft iron core concentrates the magnetic field lines, thereby increasing the magnetic field strength.

Slide 14: 

Magnetic Field around a Current Carrying Conductor : If a compass is placed in the vicinity of a current carrying conductor, the Compass needle will align itself at right angles to the conductor, Thus indicating the presence of a magnetic force.

Slide 15: 

Polarity of an Electromagnetic Coil :

Slide 16: 

1 Medical applications. ( Magnetic Resonance Imaging,CT scan etc….) 2. Magnetic Relay 3.Generate Electricity.. 4. Doorbells 5. Circuit Breaker.. 6.. Electric Bell 7.Motors 8.Speaker 9.To pull up scraps 10.Magnetic train 11.Digital slot cars… Bridging Theory in Practice

Magnetic Resonance Imaging : 

Magnetic Resonance Imaging 1) Magnetic Resonance Imaging (MRI) - A popular method of medical imaging that provides views of tissues in the body. It is a huge scanner containing a solenoid made of superconductors.

Magnetic Resonance Imaging : 

Magnetic Resonance Imaging

A Single Proton : 

A Single Proton + + + There is electric charge on the surface of the proton, thus creating a small current loop and generating magnetic moment m. The proton also has mass which generates an angular momentum J when it is spinning. J m Thus proton “magnet” differs from the magnetic bar in that it also possesses angular momentum caused by spinning.

Slide 20: 

Magnetic Moment I B F L F = IBL B L W t = IBLW = IBA m = tmax / B = IA t = m  B = m B sinq Force Torque

Slide 21: 

Angular Momentum J = mw=mvr

Slide 22: 

m = g J g is the gyromagnetic ratio g is a constant for a given nucleus The magnetic moment and angular momentum are vectors lying along the spin axis

Slide 24: 

Net magnetization is the macroscopic measure of many spins Bo M

Slide 25: 

The energy difference between the two alignment states depends on the nucleus D E = 2 mz Bo D E = h n n = g/2p Bo known as Larmor frequency g/2p = 42.57 MHz / Tesla for proton

Electromagnetic Radiation Energy : 

MRI X-Ray, CT Electromagnetic Radiation Energy

MRI uses a combination of Magnetic and Electromagnetic Fields : 

MRI uses a combination of Magnetic and Electromagnetic Fields NMR measures the net magnetization of atomic nuclei in the presence of magnetic fields Magnetization can be manipulated by changing the magnetic field environment (static, gradient, and RF fields) Static magnetic fields don’t change (< 0.1 ppm / hr): The main field is static and (nearly) homogeneous RF (radio frequency) fields are electromagnetic fields that oscillate at radio frequencies (tens of millions of times per second) Gradient magnetic fields change gradually over space and can change quickly over time (thousands of times per second)

Slide 28: 

Solenoid: Is an electromagnet with a moveable core called a plunger

2. Solenoid Uses (Relays) : 

2. Solenoid Uses (Relays)

Slide 30: 

Magnetic Relay - A device to control the switch of another circuit without any direct electrical contact between them.

3. Generating electricity : 

3. Generating electricity A generator converts mechanical energy into electrical energy using the law of induction. As long as the disk is spinning, there is a changing magnetic field through the coil and electric current is created.

4. Doorbells : 

4. Doorbells A doorbell contains an electromagnet. When the button of the bell is pushed, it sends current through the electromagnet.

Electromagnetic bell : 

Electromagnetic bell

Electric bells : 

Electric bells like the ones used in most schools also contain an electromagnet. When the current flows through the circuit, the electromagnet makes a magnetic field. The electromagnet attracts the springy metal arm. The arm hits the gong, which makes a sound and the circuit is broken. The electromagnet is turned off and the springy metal arm moves back. The circuit is complete again. Electric bells

Slide 35: 

5) Circuit Breaker - A safety device that switches off the electric supply when excessive current flows through the circuit. Uses an electromagnet to open the circuit. Normal condition The basic circuit breaker consists of a simple switch, connected to either a bimetallic strip or an electromagnet. The diagram on the left shows a typical electromagnet design. The hot wire in the circuit connects to the two ends of the switch. When the switch is flipped to the on position, electricity can flow from the bottom terminal, through the electromagnet, up to the moving contact, across to the stationary contact and out to the upper terminal.

Slide 36: 

Circuit breaker in operation The electricity magnetizes the electromagnet. Increasing current boosts the electromagnet's magnetic force, and decreasing current lowers the magnetism. When the current jumps to unsafe levels, the electromagnet is strong enough to pull down a metal lever connected to the switch linkage. The entire linkage shifts, tilting the moving contact away from the stationary contact to break the circuit. The electricity shuts off.

Slide 37: 

7) Electric Bell - The electromagnet forms the core of the electric bell. When the bell button is pressed, the circuit is closed and current flows. The electromagnet becomes magnetised, attracting the soft iron armature and the hammer strikes the gong. However, the circuit will break and the electromagnet loses its magnetism and the springy metal strip pull back the armature and the circuit is closed again. The process repeats.

Use of Electromagnetism in Motors : 

Use of Electromagnetism in Motors 1.DC motor 2. AC motor. 3.Stepper motor..

1.Motor Control : 

1.Motor Control

Slide 40: 

The D.C. Motor A direct current (DC) motor is a fairly simple electric motor that uses electricity and a magnetic field to produce torque, which turns the motor.

Slide 41: 

The D.C. Motor A split - ring commutator (sometimes just called a commutator) is a simple and clever device for reversing the current direction through an armature every half turn. The commutator is made from two round pieces of copper (held apart and do not touch each other), one on each side of the spindle. A piece of carbon (graphite) is lightly pushed against the copper to conduct the electricity to the armature. The carbon brushes against the copper when the commutator spins. As the motor rotates, first one piece of copper, then the next connects with the brush every half turn.The wire on the left side of the armature always has current flowing in the same direction, and so the armature will keep turning in the same direction.

Slide 42: 

Current in this arm flowing from left to right. Current in the same arm reverses, flowing from right to left. Current stops flowing momentarily in the coil but inertia will propel it to make contact once again, reversing the current in the coil.

Slide 43: 

To increase the turning effect on the wire coil, we can: increase the number of turns on the wire coil. increase the current in the coil. Insert a soft-iron cylinder at the center of the coil of wires.

Slide 44: 

A.C. motor An AC motor is an electric motor that is driven by an alternating current. It consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the rotating field.

Stepper Motor : 

Stepper Motor A stepper motor often has an internal rotor with a large number of permanent magnet “teeth” A large number of electromagnet "teeth" are mounted on an external stator Electromagnets are polarized and depolarized sequentially, causing the rotor to spin one "step" Full step motors spin 360o/(# of teeth) in each step Half step motors spin 180o/(# of teeth) in each step Microstep motors further decrease the rotation in each step

Full Step Motor Operation : 

Full Step Motor Operation ` Half Rotate and Hold

8.Speaker ....... : 

8.Speaker .......

To pull up scraps : 

Many objects around you contain electromagnets. To pull up scraps To pull up scraps

The German Trans-Rapid maglev train is an EMS system using electromagnets attracted to an iron “rail” : 

The German Trans-Rapid maglev train is an EMS system using electromagnets attracted to an iron “rail”

The German Trans-Rapid maglev train uses powered electromagnets attracting upward to an iron rail : 

The German Trans-Rapid maglev train uses powered electromagnets attracting upward to an iron rail

The Japanese Yamanashi demonstration maglev train uses superconducting magnets on its sides : 

The Japanese Yamanashi demonstration maglev train uses superconducting magnets on its sides

At speed superconducting magnet coils on the Japanese train induce currents in coils in the “tracks” on each side : 

At speed superconducting magnet coils on the Japanese train induce currents in coils in the “tracks” on each side

The proposed “Swiss-Metro” would link major Swiss cities by maglev trains running in evacuated tunnels. : 

The proposed “Swiss-Metro” would link major Swiss cities by maglev trains running in evacuated tunnels.

Slide 54: 

Vehicle on Guideway Linear Synchronous Motor Suspension Track Double Sided Magnet Array

Digital Slot Car Set II : 

Digital Slot Car Set II

Slide 56: 

Track This unique form of lane changing was developed using no moving parts for a low inertia and robust design. It also reduces stress encountered by the guide pin from sharp sudden changes. Digital Slot Car Set II InTrack (Intelligent Track sections) The InTrack works with the IR and electromagnetic system to minimise the amount of time and distance that the car is without power or communications. The voltage on this section of track can vary depending on which direction the car is heading. Infrared (IR) An IR indicator located in the bumper of the car triggers a sensor in the track which causes the electromagnets to energise. Electromagnets Three electromagnets are positioned on each side of the Y junction. Upon activation by the IR receivers, the electromagnets in the track will either pull the car left or right. The second electromagnet in the electromagnet array has its polarity reversed in contrast to the two outer electromagnets. This contrasting polarity creates a better flux path to pull the guide pin in the desired direction of the user. Innovations and Marketability Current switching mechanisms for digital slot cars use track witches similar to those used by model trains, where a plastic switch physically directs the guide pin to the crossover section. This unique and innovative witch removes the complications associated with moving parts by using electromagnets to allow the car to change lanes. The use of electromagnets to guide the car creates less resistance when changing lanes and allows a following car to take a different direction to the car in front at the crossover junction. The car also addresses a change in market focus from Formula One to Street Car design – allowing for new innovations to the slot car world, e.g., NOS.

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