ELECTRIC CIRCUIT TO FLEMING

Electric Circuit

A pathway that permits electrons to move in a complete circle from their source through the through resisting electrical devices and back to the source

Copper wire

the most common pathways provided for the movement of EC

Series, parallel

Types of electric circuits

Series Circuit

All circuit elements are connected in a line along the same conductor

• Supplies greater total potential difference

• Requires all resistances to be operable

Total current

(series) to the current through each circuit element

Total resistance and total voltage

In series, which elements requires to compute the sum of individual

Parallel Circuit

Elements are connected at their ends rather than lying in a line along a conductor

• Offer less total resistance to electrical current

• Not broken when a single resistance is interrupted

• Operates with greater current

• Operates at a lower voltage

Total voltage

(p) to the voltage through each circuit element

Total current and total resistance

In parallel, which elements requires to compute the sum of individual

Adding Resistances

– Total resistance drops

– Total amperage increases

– Total voltage remain unchanged

Total resistances

always less than the amount of the lowest resistor

Short circuit

Disadvantage of Parallel Circuit

Circuit breaker, Fuse

DEVICES THAT PREVENTS SHORT CIRCUIT

Circuit Breaker

Prevents short circuit

Constructed to permit the breaking of the circuit before a dangerous temperature is reached

Can be reset once the problem has been located

Fuse

Used to protect the circuit elements from overload by operating the circuit in the event of a power surge

Constructed with a metal tab that will melt when dangerously heated

Not reusable

Must be replaced

Resistor

Inhibits flow of electrons

Battery

Provides electric potential

Capacitor

Momentarily stores electric charge

Transformer

Increases or decreases voltage by fixed amount (AC only)

Diode

Allows electrons to flow in only one direction

Rheostat

Potentiometer or choke coil

A variable or precision resistor

Used to vary voltage or current

To control current

Main purpose of rheostat

Filament circuit

Location of rheostat

Electric power

1 A (current) x 1 V (voltage)

Watts

electric power is measured in?

kW

power rating

20-150 kW

X-ray Imaging System

P=IV, P=I2R

Electric power formula

Electromagnetic Induction

The production of a current in a conductor by a changing magnetic field near the conductor

Basis of transformer operation

Michael Faraday

He described the first law of electromagnetic induction

He observed the current in a changing magnetic field

Faraday Experiment

Changing magnetic field induces current

Magnetic field generates electricity

Ammeter

measures current

First Law of Electromagnetic Induction

It states that an electric current is induced in a circuit if some part of that circuit is in a changing magnetic field

Strength of magnetic field, velocity of MF as it moves past the conductor, angle of the conductor to the magnetic field, number of turns in conductor

Faraday Law

Directly proportional

relationship of strength, velocity, number of turns

90 degree

angle of conductor

Move the conductor, move magnetic lines of force, Vary the MF Strength

THREE WAYS TO INDUCED ELECTRIC CURRENT IN THE CONDUCTOR

Hans Oersted

He demonstrated that electricity can be used to generate magnetic fields

Oersted Experiment

Moving or spinning charges induces magnetic field

Electricity generates magnetic field

Heinrich Lenz

He described the second law of electromagnetic induction

Second Law of Electromagnetic Induction

states that induced current flow sets up a magnetic field opposing the action that produced the original current

Self induction, mutual induction

TWO TYPES OF INDUCTION

Self induction

The production of current within a conductive coil opposing the magnetic field that induced it

Autotransformer, choke coil/ rheostat

examples of self-induction

Mutual Induction

The production of a current in a neighboring circuit

Occurs when two coils are placed in proximity and a varying current is applied to the first coil induces a similar flow in the second coil

High voltage transformer, Filament transformer

examples of mutual induction

John Fleming

He developed a series of easily remembered aids to help with the relationship between the electricity and magnetism

Hand thumb rule along conductor, Hand thumb rule for solenoid and electromagnetic poles, hand generator effect rules, hand motor principle rules

Fleming‘s Right Hand Rules

Along a conductor

THUMB: conventional current or electron flow

FINGERS: magnetic field

Solenoid and Electromagnetic poles

THUMB: direction of north pole

FINGERS: conventional current or electron flow

Generator Effect

THUMB: movement of conductor

INDEX FINGER: magnetic lines of force field

MIDDLE FINGER: current or electron flow

Motor Principle

THUMB: movement of conductor

INDEX FINGER: magnetic lines of force field

MIDDLE FINGER: current or electron flow