Key points on Electricity and Magnetism

ELECTRICITY AND MAGNETISM 

Hello guys I'm Swift (Science Lair)  it has been long since I posted anything, but today i would be taking you through the aspects of electricity and magnetism
Lets start with the definition of an electric field

Electric Field is a region where a small positive charge experiences a force.

Electric Current is the rate of flow of charge.

EMF (electromotive force) is the work done by a cell when a unit positive charge to move rounds the circuit.

PD (potential difference) is the energy converted from electrical form to non electrical (heat) form when a unit positive charge moves between two points.

Voltage = Current × Resistance = IR



Note: When the current in the electric circuit increases, it’s temperature increases, and then it will cause its resistance to increase. Current IncreaseàTemperature increaseàResistance increase

Electromagnetic induction is the phenomenon of producing an emf in a circuit due to changing magnetic field. Faraday’s Law of Induction: the emf generated in a conductor is proportional to the rate of change of magnetic flux linking the circuit.

Lenz’s Law: the direction of the induced emf and hence the induced current in a closed circuit is always such as to oppose the change in magnetic flux producing it.

Ways to increase emf in solenoid:

1. Using a stronger magnet.
2. Increasing the speed of moving the magnets.
3. Increasing the number of turns on the coil.

Ways to increase force in motor

1. Increasing number of turns in the coils
2. Increasing a stronger magnet
3. Including a soft iron inside the coil
4. Increasing current

Ways to increase emf in a.c. generator
1. Decreasing distance between the magnet and coil.
2. Using a stronger magnet.
3. Increasing speed of moving the magnets
4. Increasing number of turns in the coil.

Operation of Transformer

1. Alternating current is supplied to primary coil.
2. Alternating current causes iron core to magnetise and magnetic field to change.
3. Magnetic fields follow iron core and link to secondary coil.
4. Hence emf is induced in secondary coil by electromagnetic induction.

Flemings Left Hand Rule is used for motor where current is used to produce motion. Flemings Right Hand Rule is used for generator where current is produced using motion.

Thermionic emission: When metals are heated some of the free electrons get sufficient energy to escape from the metal surface. This phenomenon is known as thermionic emission.

Radioactivity is a property of some substance where alpha, beta and gamma radiation occurs by breaking of nucleus.

Radioactive decay is the breaking of nucleus to emit alpha (helium nucleus), beta (electron) and gamma(high frequency electromagnetic wave).

Random decay means we cannot predict the nucleus which will decay next.

Spontaneous decay means the decay is unaffected by physical condition like pressure, force, temperature etc.

Half life is the time taken for radioactive substance to decay into half.

Background Radiation is the radiation occurs by the surroundings.

Origin of background radiation: Cosmic ray, Sun, Radioactive rocks in the Earth

Precautions when handling radioactive substances

1) Radioactive substances should not be touched.
2) Wear radiation protective suits

3) Using long forceps