Given by Michael faraday.
The production of an electromotive force across an electrical conductor in a changing magnetic field.
A galvanometer is a device that detects the presence of current and also shows the direction of the current.
Emf is only produced/induced as long as the magnetic field is consistently changed.
A static magnetic will not cause induction.
There should be a relative motion between the magnetic field and the wire/loop/coil.
If a moving solenoid into the magnet is back and forth, the number of field lines passing through the coil will either increase or decrease.
This will cause E.M.F which in turn causes the galvanometer to deflect.
The direction of the E.M.F produced is consistently changing when we are pushing the magnet in and Pulling it out. The magnitude of the induced emf increases if:
• A stronger magnet is used.
• The number of turns of the coil is increased.
• The magnet and the coil are moved with respect to each other at a faster rate.
• Increasing the cross-sectional area of the solenoid.
The faster the relative motion, the greater the emf produce.
Lens'z law:
The direction of a current produced by an induced emf opposes the changing producing it
Whenever a current passes through the solenoid a magnetic field is set up.
The current always produces in a direction that goes against the change that produces EMF.
Chemical energy → mechanical energy → electrical energy
AC generator
Mechanical energy → electrical energy.
It consists of a rectangular coil of wire placed between the poles of two permanent magnets. The coil is rotated about an axis.
EMF is induced between the ends of the coil. Carbon brushes reduce friction.
When there was a current-carrying conductor placed between the poles of a magnet we use the left-hand rule to determine its direction.
In an AC generator, we find its direction by the Right-hand rule.
AC generator output:
As the coil is vertical the emf is zero.
When the coil is horizontal the emf is maximum.
The current that we get at the output continuously changes its direction which is why it's known as AC.
An alternating current is defined as the periodic reverse direction of a current which changes its magnitude continuously with respect to time.
Transformers
A transformer is an electrical device that can be used to increase or decrease the voltage of an alternating.
It makes use of electromagnetic induction.
A transformer consists of two coils of wire wrapped around a soft iron core.
Voltage is changed by having a different number of turns in the primary and secondary coils.
Current passes through a primary coil. This primary coil will generate a magnetic field and pass through the secondary coil. This change will produce emf and a current will be produced.
There must be a changing magnetic field so AC current is used.
Step-down transformers are those whose voltage decrease as it passes through the transformer because the number of turns in the secondary coil is less than in the primary coil.
Step-up transformers are those whose voltage increases as it passes through the transformer.
The higher the current in a cable, the greater the energy loss by heating.
The national grid uses step-up transformers to increase the voltage from power stations to thousands of volts.
This lowers the current in transmission cables. Step-down transformers are then used to decrease the voltage from the transmission cables.
It is now safe to distribute to homes and factories.
Cathode Rays oscilloscope
A stream of electrons leaving the negative electrode in a discharge tube containing a gas at low temperature and pressure is called a cathode ray.
An oscilloscope is a device that can be used to study rapidly changing signals such as a soundwave or an alternating current.
When any rapidly changing signal is converted to an electrical signal, it can be demonstrated on the screen of an oscilloscope.
In an ideal transformer power of the input is equal to the power of the output no energy loss took place.
