Electrostatics, Electricity & Magnetism Flashcards
Definition of Electrostatics
A study of stationary electric changes
Use of Electrostatics in Medicine:
ECG (electrocardiography)
Defibrillator
Electric charge (q): SI unit
Charge SI Unit : Coulomb (C)
Electric charge (q): Possible Types
Negative / Positive
Electric charge (q): Elementary Charge Value
= 1.6 *10^-19 C
What are charge carriers?
Particles with electric charge
What are 5 examples for the most basic charge carriers?
Electron Proton Atoms - (overall Neutral) Cations (Positive) Anions (Negative)
Coulombβs Law: What does it say? (in words)
Gives the Coulomb force (F) of electrical interactions between two electrical bodies q. r is the distance between the two bodies.
Coulombβs Law: Formula
πΉ=πβ(π1βπ2)/π^2
What is the value and unit of coulombβs constant (k)?
k = Coulombβs constant= 9*10^9 N(π^2)/πΆ^2
What is an Electric field?
Model for interpreting electric interactions.
Defined by the force acting on an charge in a point at the field space.Field lines are used to show the electric field range and direction.
What are the properties of a Homogeneous Electric Field?
Any point in Field is with same strength and direction.
Field Lines are Parallel.
What are the properties of a Non- Homogeneous Electric Field?
NOT Any point in Field is with same strength and direction.
Field Lines are NOT Parallel.
What is an Electric dipole?
Electric dipole: Two charges at a given distance (d) apart, with the same magnitude and opposite signs (q)
What is a dipole Field?
Dipole field: The electric field of an electric dipole. It has inhomogeneous field lines.
What is formula for Electric dipole moment (p)?
Electric dipole moment (p):
π=πβπ
What is the SI unit for Electric dipole moment (p)?
Dipole Moment unit -[Coulomb*meter] or [C/m]
What is Electric field strength (E)?
The force F acting on a unit of positive charge. It is a vector quantity.
What is the Formula for Electric field strength (E)?
πΈ=πΉ/π
What is the Unit for Electric field strength (E)?
Electric field strength Unit: N/C or V*m
What is Voltage (U)?
The work we need to move a unit charge from point 1 to 2 against the electrical field. βU(12)β
What is the formula for Voltage (U)?
Basic Formula in Electrostatics
π= π/π
What is the SI Unit for Voltage (U)?
Voltage unit: Volt (V) = J/C
What is Electric potential (π)?
The work per unit of charge needed to move a charge from a reference point to another specific point (i). Note: The π(i)=π_ππ (voltage between point 0 and i).
What is Electric potential Difference (Ξπ) equal to?
The potential difference is the same as the voltage.
As in the potential difference between point 1 to point 2 is equal to the Voltage βU(12)β
What is an Equipotential surface?
The set of all points, which has the same electric potential value. The equipotential surface are 90 degrees to the field lines.
What is a Capacitor?
Generally
Capacitor: An electronic component with two terminals (plates), capable of storing electrical charge and energy by generating an almost homogeneous electrical field between the plates.
What is a Parallel Plate Capacitor? and what is formula for its potential difference?
The simplest form of a Capacitor. The potential difference (U) depends on the electrical field strength (E) and the distance between the plates: (π=πΈβπ)
What is a Capacitance?
A measure of a capacitors ability to store charge
What is the formula for Capacitance?
πΆ= π/π
What is the SI unit for Capacitance?
Capacitance Unit : Farad (F)
C/V
The electric energy stored in the capacitor: is equal to the ______ (__) needed to charge the capacitor.
The electric energy stored in the capacitor: is equal to the WORK (We) needed to charge the capacitor.
What is the formula for Capacitor Electrical Energy Stored?
π= (1/2)β(π^2/πΆ)=1/2βπΆβπ^2
or π= 1/2βπΆβπ^2
Considering a Parallel Plate Capacitor: For With increased electrical charge being transferred to the plates, the electrical ____ will be even stronger .
Considering a Parallel Plate Capacitor: With increased electrical charge being transferred to the plates, the electrical FIELD will be even stronger .
Connecting capacitors in a circuit (2 or more capacitors):
Formula when In SERIES?
1/πΆ=1/(πΆ1) +1/(πΆ2)
Connecting capacitors in a circuit (2 or more capacitors):
Formula when In PARALLEL?
πΆ=(πΆ1)+(πΆ2)
A ________ is used to deliver shock to a patient in cardiac arrest with a shockable rhythm to restart the patientβs heart.
A DEFIBRILLATOR is used to deliver shock to a patient in cardiac arrest with a shockable rhythm to restart the patientβs heart. (βEliminating Fibrillationsβ)
One of the main components of a defibrillator is the ________. The ________ stores large amount of energy as electrical charge in the plates.
One of the main components of a defibrillator is the capacitor. The capacitor stores large amount of energy as electrical charge in the plates.
What is an Electric circuit?
A circuit consisting of electrical components (such as resistors, capacitors, voltage sources).
What is an Electric Current (I)?
The motion of electrically charged particles. It is a physical quantity and it is the amount of electric charge flowing through a cross section in a unit time
What is the formula for Electric Current?
πΌ= βπ/βπ‘
What is the SI Unit for Electric Current?
SI unit for Electric Current (I): Ampere (A)
What is the value of Direct current (DC) over time?
The current is constant over time
What is the value of Alternating Current (AC) over time?
The current change as a sine function over time
What is an Electric insulator? What does it allow for?
No free movement of charge carrier particles in a material.
What is an Electric Conductor? What does it allow for?
Free movement of charge carrier particles in a material.
What is Ohmβs Law?
The electric current flowing in a conductor is proportional to the voltage between the two poles.
What is the formula for Ohmβs Law?
U=RβI
U - Voltage (sometimes denoted V)
R - Resistance
I - Electric Current
What is Electrical Resistance(R)?
The ratio of voltage between 2 points and the current flowing through it. Defined in the most simplified way by Ohmβs Law.
How can Resistance (R) be defined by Ohmβs Law?
Give the Formula!
R=π/πΌ
What is the SI unit for Resistance?
Resistance SI unit: Ohm (β¦). 1β¦ = 1V/A
What is definition of resistance from the aspect of material properties? (not Ohmβs Law)
Resistance of a conductor depends on type of material and its dimensions. Which are:
l = length
A = cross-sectional area
π = resistivity
How can Resistance (R) be defined by material properties?Give the Formula!
R=πβπ/π΄
l = length
A = cross-sectional area
π = resistivity
What is Resistivity (π)?
Also called specific resistance. A proportionality constant specific to the material of the conductor.
What is the unit for Resistivity (π)?
Resistivity Unit: β¦βm.
What is Electrical Conductance (G)?
Is the inverse to electric resistance.
What is the Formula for Electrical Conductance (G)?
πΊ= 1/π
What is the SI Unit for Electrical Conductance (G)?
Electrical Conductance SI unit: Siemens (S)
What is Conductivity(π)? What is the medical importance of it?
Also called Specific Conductance. Physical quantity specific to a conductor material. E.g. In the body, the specific conductivity (also resistivity) of human tissues are different depending on the tissue. Muscle has a high conductivity, while bone has a low.
What is the SI Unit of Conductivity(π)?
Conductivity SI unit: S/m
What is the Formula for Conductivity(π)?
π= 1/π
What is the formula describing connection of resistors in series?
π eq=π 1+π 2+β―+π π
What is the formula describing connection of resistors in parallel?
1/(π ππ) =1/(π 1) +1/(π 2) +β―+1/(π π)
What is the Joule heating (aka Work of Electric Current)?
It is the work performed by the electric field to move electric charged particles through the given voltage containing circuit.
What is the Formula for Joule heating (aka Work of Electric Current)?
π=πβπΌβπ‘
What is the formula for Work of electric current?
Joule
What is the Formula for Electrical Power (P)?
π=πβπΌ
What is the Unit for Electrical Power (P)?
Power Unit: W (Watt)
which is Joule per Second
What is the use for Kirchhoffβs Laws?
In electricity
Describes the distribution of current and voltage through the circuit.
What is the Kirchhoffβs current law (Kirchhoffβs 1st law)?
Based on conservation of electric charge. The sum of all current going into a junction equals the current going out of the same junction.
What is the Formula of Kirchhoffβs current law (Kirchhoffβs 1st law)?
βπΌππ= (πΌ1)+(πΌ2)=βπΌππ’π‘=(πΌ3)+(πΌ4)
What is the Kirchhoffβs voltage law (=KirchhoffΒ΄s 2nd law)?
Based on conservation of energy. All the potential difference in the circuit equals 0.
What is the formula of Kirchhoffβs voltage law (=KirchhoffΒ΄s 2nd law)?
βπ=0
What is a RC circuit?
A circuit consisting of a resistor and a capacitor.
What is an AC circuit?
A circuit consisting of periodically changing current and voltage. It change with a sine function over time.
What is the advantage of using a Capacitor in an AC circuit?
In an AC circuit, alternating current is continuously charging and discharging the capacitor with alternating electrical polarity. Therefore, it has a finite resistance, which is called its called capacitive reactance (Xc).
What is the formula for capacitive reactance (Xc)?
πc=1/(π*πΆ)
π = angular frequency of AC
Why it isnβt useful to have a capacitor in a DC circuit?
A capacitor will not work in a DC circuit, since the capacitor will have an infinite resistance.
It will work as a break in the circuit - no good.
What is Electric Impedance (Z)?
Impedance (Z): The βtotalβ resistance in a circuit consisting of a capacitor and a resistor (RC) is the sum of the resistance through the capacitor (Xc) and the resistance (R) through the resistor.
To find Z, we need to take the vector of R and XC, when they are assumed to be ________ to each other. We can use the Pythagoras principle to calculate it
To find Z, we need to take the vector of R and XC, when they are assumed to be perpendicular to each other. We can use the Pythagoras principle to calculate it
To find Z, we need to take the vector of R and XC, when they are assumed to be perpendicular to each other. We can use the ________ principle to calculate it
To find Z, we need to take the vector of R and XC, when they are assumed to be perpendicular to each other. We can use the Pythagoras principle to calculate it
Calculation of Impedance (Z) in Series RC circuit:
π^2=(π ^2)+(π^2)
Calculation of Impedance (Z) in Parallel RC circuit:
(1/π)^2=(1/π )^2+(1/πc)^2
What are Electrodes?
An electrical conductor (metallic part) connecting to the non-metallic part of the circuit (e.g. solutions, body tissue).
What is an Anode?
An Electrode that attracts negatively charged ions from the non-metallic solution.
What is an Cathode?
An Electrode that attract positively charged ions from the non-metallic solution.
ECG and defibrillators contain ________ needed to connect the body around the heart to the circuit.
ECG and defibrillators contain electrodes needed to connect the body around the heart to the circuit.
In chemistry, a classical example for use of electrodes is the ________ ____ (the electrodes connect the non-metallic part, which is the electrolyte solution to the circuit).
In chemistry, a classical example for use of electrodes is the Galvanic cell (the electrodes connect the non-metallic part, which is the electrolyte solution to the circuit).
What is a Magnet?
A body with magnetic property. It contains two poles (northern and southern).
What is a Permanent magnets?
The magnet contains a large quantity of iron, nickel or cobalt, creating its own persistent magnetic field.
What is a Electromagnets (also called temporary magnets)?
A conductor produces a magnetic field when electric current flows through. If there is no current, it will be no magnetic field.
What is a Magnetic interaction?
The magnets interact with each other by exerting forces. Two like poles (e.g. south pole β south pole) Repel from each other. Opposite poles will attract each other.
What is Magnetic moment (m/Β΅)?
physical quantity used to describe the magnetic strength. Electrons, protons and neutrons also has magnetic properties (Lecture 6).
What is a Magnetic field?
The magnets creates a field around themselves, and they use this field to exert forces on each other.
What is a practical medical use of Magnetism?
MRI - The patient is placed into a strong magnetic field. All the hydrogen ions in the body will align according to the magnetic field lines. During the measurement, we gather information about the patient by investigating the changes in net magnetic moment.
What is Magnetic flux density (B)?
Characterizes the strength of a magnetic field and the force acting on a magnet in an external magnetic field. The magnetic flux density is proportional to the electrical current.
What is unit for Magnetic flux density (B)?
SI unit: Tesla (T)
Magnetic effect of _______ _______ are the basis of electromagnets.
Magnetic effect of electric current are the basis of electromagnets.
What is the Advantage of electromagnets?
The magnetic field can be switched off, we can control the magnetic strength by changing the electric current, the magnetic field is strong and homogeneous.
What is Electromagnetic induction?
A moving magnetic field, generates an electric field.
What are Electromagnetic oscillations?
Contains both changing electric and magnetic fields.
What is Self induction?
Voltage is induced in the same coil, when current change, the magnetic field will change.
What is a LC circuit (also called a resonant circuit)?
Consist of a an inductor (L) and a capacitor (C).
LC circuit is an example of ____ induction.
LC circuit is an example of self-induction.
LC circuit contains ____ ohmic resistance.
LC circuit contains ZERO ohmic resistance.