# Magnetism

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A series of free Online High School Physics Video Lessons.

In this lesson, we will learn

• Ampere's Law
• Solenoids - Electromagnets
• Electromagnetic Induction
• Transformers - Power Transmission

### Ampere's Law

Ampere's Law was discovered in 1819 by Ampere. Ampere's Law states that currents generate magnetic fields or in other words, whenever you have a current, there is a magnetic field circulate around it. Ampere's Law is expressed in the equation
magnetic field × 2(pi) × radius = constant × current(passing through that path).

How to use ampere's law to derive the formula to calculate the magnetic field of a wire and the magnetic field of a solenoid?
How to calculate the magnetic field of a solenoid given the electric current and the number of turns in the solenoid?
Example:
A 5 cm long solenoid has 1500 turns of wire and carried a current of 7.0 A. Caluculate the strength of the magnetic field at the center of the solenoid.

### Solenoids - Electromagnets

Solenoids is a configuration of wires wrapped in a mass of loops that creates a magnetic field in a given direction which is used as the basis for electromagnets, or temporary electricity driven magnets.
Understanding solenoids and electromagnets.
How to make a simple electromagnet using a battery, wire and iron nail or other iron core?

The Faraday - Lenz law states that when you have change in magnetic flux, you generate electromotive force. The formula to determine the Faraday - Lenz law is
magnetic flux = magnetic field × area.

This video demonstrates the Faraday's Law and Lenx's Law

### Electromagnetic Induction

Electromagnetic induction is the concept of changing in one current induces changes in another current. This results in the production of voltage through magnetic field described in Ampere's Law. The right hand rule is applied to the induced current. The concept of electromagnetic has led to power transmission.

The concept of electromagnetic induction and its features. This episode is an introduction to electromagnetic induction. The presentation is supported by many experimental demonstrations.
The video covers the following topics:
1. Oersted's discovery of the magnetic effect of an electric current (sometimes called the "motor effect" as it is the principle behind simple DC motors);
2. Faraday's discovery of electromagnetic induction;
3. Magnetic flux;
5. Faraday's law of electromagnetic induction;
6. Lenz's law (or Lenz's rule);
7. Eddy currents and their braking effect.

### Transformers - Power Transmission

Transformers are used to change a current into another current. Step up transformer increases the voltage and step down transformer decreases the voltage. In power transmission, which is power transmitted through wires over large distances, there is a power loss due to the resistance caused by (I2)R heating, step up transformer is needed to pump up the voltage using AC.

Understanding transformers and power transmission. A brief video detailing the key points regarding the operation of electrical transformers. The video discusses electromagnetism, induction and the transformer formula.

Try the free Mathway calculator and problem solver below to practice various math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.