Electromagnetism Grade 11

Joules

Energy is measured in _____

Watts

Power is measured in ____

Coulombes

Charge is measured in ______

Amperes

Current in measured in _____

Volts

Voltage is measured in ______

Ohms

Resistance is measured in _________

Kirchoffs Current Law

At any junction point, the current coming in equals the current coming out.

Kirchoffs voltage law

Around any one path, the sum of the voltages lost is equal to the voltage across the battery. I.E Voltage across all paths is equal.

Ohms Law

The total resistance of any circuit is the ration of the voltage across the artery and the current being drawn by the battery.

Basic principle of Electromagnetism

Whenever there is current in a conductor, a magnetic field is created in the region around the conductor.

Right Hand Rule for a Straight Conductor

Thumb in the direction of the current, fingers wrap in the direction of the magnetic field.

Right Hand Rule for a Solenoid

Curl the fingers of the right hand in the direction of the current, thumb will point to the north.

Magnetic Field Strength of a solenoid or an Electromagnet

Determined by the number of coils, the amount of current, and magnetic permeability of the core material.

Ferromagnetic

High magnetic permeability, increases strength of an electromagnet. “Soft Iron,” such as Fe, Co, and Ni

Paramagnetic

Can rarely be magnetized, and only slightly increase the strength of an electro magnet, Eg, Aluminium and Air

Diamagnetic

Cannot be magnetized under normal conditions and decrease an electromagnets strength. Eg Cu, H2O

The Motor Principle

Whenever a current carrying conductor is placed in a magnetic field the conductor experiences a magnetic force, and thus moves. This force is perpendicular to both the external magnetic field and direct that the current is travelling.

Right Hand Rule for the Motor Principle

Finger Field Thumb Current Palm Force

Battery, no

Which part is A and does it spin?

Split Ring commutator, Yes

Which part is B and does it spin?

Brushes, no

Which part is C and does it spin?

Magnets, no

Which part is D and does it spin?

Armature, yes

Which part is E and does it spin?

Generator Effect

Whenever a magnetic field in the region around a conductor is moving or changing in strength, a current is induced to flow through the conductor.

Lenz’s Law

The induced current flow in such a direction that the induced magnetic field opposes the action of the opposing field.

Transformer

The main benefit of AC vs DC currents?

1. Spin faster (Greater FA) 2. More turns in the coil 3. Stronger external magnets $. Ferromagnetic core

To increase the output of a generator

High voltage

Most efficient way to transport electricity.