# Get the Knowledge that sets you free...Science and Math for K8 to K12 students

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## Basic Concepts

EML [Electromagnetic Launcher] Spacecrafts burn lakhs of gallons of fuel to reach orbit. If the rocket has to be launched from moon, it is not possible to launch using traditional methods. So the rocket engineers at the Marshall Space Flight Center are investigating whether Electromagnetic power can do the job. It would be a much cleaner, safer and cheaper way of launching vehicles. As the rocket rises past each electrical coil inside a long vertical tube, it accelerates faster. Lets learn the working principles behind this new rocket launcher in this topic.

## After completing the topic, the student will be able to:

• Understand the need of electromagnetism based on its daily life applications.
• Investigate the magnitude of the magnetic field produced by a straight current–carrying conductor using Oersted's experiment.
• Explore the direction of the magnetic field produced due to a current in a long conductor using Oersted′s right hand rule or Maxwell′s corkscrew rule.
• Calculate the magnetic flux at a point P due to a circular current carrying coil using Biot– Savart's law and its applications in finding the poles in a magnetic field.
• Demonstrate the force between two parallel conductors using Ampere's law and investigate its applications.
• Discover the working of solenoid and its importance in various applications to develop uniform magnetic field, also probe for the applications of electromagnetism like magnetic levitation etc.
Induction motor. This type of alternating current (AC) motor comprises a static stator (pale grey casing), which contains electromagnets (blue) arranged to form a hollow cylinder. Within the stator sits a moving rotor (shiny), which is mounted on the motor′s shaft. The rotor also contains electromagnets (not seen). To make the rotor turn, the magnetic field of the stator is altered so that the poles of the rotor are attracted by the opposite poles on the stator. As the magnetic field of the stator rotates, the rotor is forced to rotate with it.
Introduction

Electricity and magnetism go hand in hand. Wherever there is moving electric charge, magnetic effects are present too. Electromagnetism is the physics of the electromagnetic field; it is encompassing all of space, composed of electric and magnetic fields.

Electric field can be produced by stationary electric charges, and gives rise to the electric force, which causes static electricity and drives the flow of electric current in electrical conductors. The magnetic field can be produced by the motion of electric charges, such as an electric current flowing along a wire, and gives rise to the magnetic force one associates with magnets.

The term "electromagnetism" comes from the fact that the electric and magnetic fields are closely intertwined and under many circumstances, it is impossible to consider the two separately. For instance, a changing magnetic field gives rise to an electric field; this is the phenomenon of electromagnetic induction, which underlies the operation of electrical generators, induction motors, and transformers. Oersted was the first scientist to show how a magnetic compass needle deflected due to the presence of an electric current. The reverse is true as well!

We use electromagnets to generate electricity, store memory on our computers, generate pictures on a television screen, diagnose illnesses, and in just about every other aspect of our life that depends on electricity.

Basics - A quick look
Oersted's experiment Biot–Savart's law Ampere's circuital law Solenoids
An electric current produces a magnetic field. This was first discovered by Oersted in 1820. Biot–Savart law gives the magnetic field at a certain point near a current carrying conductor. Discovered by Andre–Marie Ampere in 1826, relates the integrated magnetic field around a closed loop to the electric current passing through the loop. A solenoid is a coil of wire, often wrapped around a soft iron core. When electric current is passed through the wire, the solenoid produces a magnetic field.
Take a wire and connect it to a battery and a key. Keep a compass needle on one side. Note its initial position. As soon as you pass a current through the wire, the compass needle will show a deflection. As long as the current is passing through the wire, the compass needle will stay deflected. The Biot–Savart law relates the magnetic fields to the electric currents, which are their sources. In a similar manner the Coulomb's law relates electric fields to the point charges which are their sources. Ampere's law gives another method to calculate the magnetic field due to a given current distribution. Ampere's law may be derived from the Biot–Savart law and Biot–Savart law may be derived from the Ampere's law. However, Ampere's law is more useful under certain symmetrical conditions. When the turns are closely spaced, each can be approximated as a circular loop, and the net magnetic field is the vector sum of the fields resulting from all the turns. One end of the solenoid behaves like the north pole and the opposite end behaves like the south pole.