Electrostatics and Electromagnetism

Question 1

It states that like charges repel each other and unlike charges attract each other.

Answer 1

1st Law of Electrostatics

Question 2

This states that the force of attraction or repulsion between charges is directly proportional to the product of two charges and inversely proportional to the square of the distance between them

Answer 2

2nd Law of electrostatics

Question 3

What is the formula for the force of attraction between charges?

Answer 3

F = k • (Q1 • Q2) / d^2 (Newton)

where k= 1/(4πεoεr)

Question 4

How much is the absolute permittivity (εo)?

Answer 4

8.854 x 10^-12 Farad per meter

Question 5

What is the relative permittivity (εr) in free space?

Answer 5

1

Question 6

What is the value of k in free space or air (SI Units)?

Answer 6

9 x 10^9

Question 7

1 coulomb = _______ statcoulomb or electrostatic units (ESU)

Answer 7

3x10^9

Question 8

1 Newton = ____ dynes

Answer 8

1x10^5

Question 9

This is an electric potential resulting from the location of charged bodies in the vicinity

Answer 9

Electrostatic Potential

Question 10

What is the formula for Electrostatic/Electric Potential?

Answer 10

V = Q / (4πεoεrd) ; volts

Question 11

1 volt = ___ joule/coulomb

Answer 11

1

Question 12

This is the work done in moving one electron (sometimes called an elementary charge) in a field with a potential difference of 1 volt.

Answer 12

Electron Volt (eV)

Question 13

1 eV = ________ joule

Answer 13

1.6 x 10^19

Question 14

The _________ between two points in an electric field is the amount of work needed to take a charge of 1C from one of the points to the other.

Answer 14

Potential difference

Question 15

The ______________at any point within an electric field is given the force experienced by a positive charge of one coulomb placed at that point and is a vector quantity.

Answer 15

Electric Field Strength/Intensity

Question 16

What is the formula for Electric Field Intensity?

Answer 16

E = (k • Q2) / d^2

Question 17

What will happen to an insulating medium with voltage more than breakdown voltage is applied?

Answer 17

It will get punctured.

Question 18

This is defined as the total number of electric lines of force emanating from a charged body.

Answer 18

Electric Flux (Ψ)

Question 19

This is represented by an electric flux.

Answer 19

Electric Field

Question 20

This is defined as the amount of flux passes through unit surface area in the space imagined at right angle to the direction of electric field.

Answer 20

Electric Flux density

Question 21

What is the formula for Electric Flux density?

Answer 21

D = εoεrE
= Ψ/(4πr^2)

Where Ψ is equal to the Q (charge)

Question 22

It states that the total flux out of a closed surface is equal to the net charge within the surface.

Answer 22

Gauss’ Law

Question 23

What is the formula for Gauss’ Law

Answer 23

Q = D x Area of the Surface

Question 24

It is the measure of how well a capacitor can store electrical charges.

Answer 24

Capacitance

Question 25

This is any device on which electric charges can be stored so as to possess electric potential. It consists of two conducting plates separated by a layer of an insulating medium called dielectric.

Answer 25

Capacitor

Question 26

It is the unit of capacitance. it is one coulomb of charge on the plate/s raising its potential difference by one volt.

Answer 26

Farad (F) C = Q/V

Question 27

What is the formula for the capacitance of parallel-plate capacitors.

Answer 27

C = (εo•εr•A) / d where d is the thickness of dielectric medium and A is the area of each plate

Question 28

Formula for the capacitance of n-plate capacitor

Answer 28

C = (n-1) • (εo•εr•A) / d where d is the thickness of dielectric medium and A is the area of each plate

Question 29

What is the formula for the capacitance of multi-plate capacitor with different dielectrics.

Answer 29

C = (εo•A) / [ (d1/εo1) + (d2/εo2) + ... + (dn/εon) ]

Question 30

A circuit has two capacitances connected in series. How do you compute for the total capacitance

Answer 30

1/Ct = 1/C1 + 1/C2

Question 31

What is the formula for Capacitance?

Answer 31

C = Q/V

Question 32

Two capacitors are connected in Parallel. How do you compute for the total capacitance?

Answer 32

Ct = C1 + C2

Question 33

What is the formula for the total energy stored in a capacitor?

Answer 33

W = (CV^2)/2 = QV/2 = Q^2 / 2C

Question 34

It is the reciprocal of capacitance.

Answer 34

Elastance

Question 35

It states that whenever the flux linking a coil or current changes, an emf is induced in it.

Answer 35

First Law of Faraday's Law of Electromagnetic Induction

Question 36

It states that the magnitude of the induced emf is proportional to the rate of change of flux linkages.

Answer 36

Second Law of Faraday's Law of Electromagnetic Induction.

Question 37

This is defined as the phenomenon in which a change in electric current in a circuit produces an induced electro-motive force in the same circuit.

Answer 37

Self-Inductance

Question 38

It is a two terminal device that consist of a coiled wire wound in common core or in free air.

Answer 38

Inductor / choke coil

Question 39

Unit of inductance

Answer 39

Henry

Question 40

What is the formula for the voltage in an inductor?

Answer 40

V = L (di/dt)

Question 41

What is the total inductance for inductors connected in series?

Answer 41

Lt = L1 + L2 + ... + Ln

Question 42

What is the total inductance for inductors connected in parallel?

Answer 42

Lt = 1 / [ (1/L1) + (1/L2) + ... + (1/Ln) ]

Question 43

It is the condition of inducing an emf in a coil or conductor by magnetic flux lines generated in another coil or conductors.

Answer 43

Mutual Induction

Question 44

It is the amount or degree of mutual induction that exists between two coils or windings.

Answer 44

Mutual Inductance

Question 45

What is the formula for the Energy stored in an Inductor

Answer 45

W = 1/2 LI^2

Question 46

It is the space surrounding the magnet, where the magnetic effect is experienced.

Answer 46

Magnetic Field

Question 47

This is the lines of force produced by a magnet.

Answer 47

Magnetic flux (Φ) ; maxwell or weber

Question 48

1 line of force = ___ maxwell

Answer 48

1

Question 49

1 weber = ______ maxwells

Answer 49

1 x 10^8

Question 50

This is the flux that does not follow the intended path in a magnetic circuit.

Answer 50

Leakage Flux

Question 51

This is the number of magnetic lines per unit area

Answer 51

Magnetic flux density

Question 52

What is the formula for Magnetic Flux Density (B)

Answer 52

B=Φ/Acosθ ;Tesla or Gauss where θ is the angle between the normal to the surface and a magnetic field vector

Question 53

1 Tesla = ______ Gauss

Answer 53

10,000

Question 54

It is the ability of a material to conduct magnetic flux through it.

Answer 54

Permeability (μ)

Question 55

What is the formula of Permeability?

Answer 55

μ = μo • μr = B/H ; Henry per meter where μo is the absolute permeability and μr is the relative permeability

Question 56

What is the value of Absolute permeability (μo) or the permeability of vacuum air (reference medium)

Answer 56

4 x 10^-7 H/m

Question 57

It is the ratio of permeability of a given material to the permeability of vacuum of air.

Answer 57

Relative Permeability (μr)

Question 58

It is the force experienced by a unit north pole at that point. It is also called magnetizing force or magnetic potential gradient.

Answer 58

Magnetic Intensity (H)

Question 59

What is the formula for Magnetic Intensity (H)?

Answer 59

H = Force / Magnetic Pole Strength = Newton/Weber = (Number of Turns • Ampere) / mean length of flux lines (meter) = Magnetomotive Force (Ampere-turn) / mean length of flux lines

Question 60

This is the cgs unit of magnetic field strength. It is equal to gilbert per centimeter.

Answer 60

Oersted

Question 61

For magnetic flux, we use the __________ rule.

Answer 61

Right Hand Rule

Question 62

For the right hand rule, the thumb indicates the direction of ________.

Answer 62

Current

Question 63

For the right hand rule, the curled fingers indicates the direction of __________.

Answer 63

Magnetic Flux density

Question 64

What is the formula for the force on a conductor carrying a current in a magnetic field

Answer 64

F = BILsinθ

Question 65

What is the formula for the Force between current carrying parallel conductors

Answer 65

F = (2x10^-7) • (I1•I2) / (L/D)

Question 66

This is the driving force required to drive the magnetic field through a magnetic circuit by passing an electric current (I) through a number of turns.

Answer 66

Magnetomotive force

Question 67

What is the formula for magnetomotive force?

Answer 67

mmf = NI (SI, Ampere-turns) | = 0.4πNI (cgs, Gilberts)

Question 68

This is the property of a magnetic material to oppose the flux from penetrating the material.

Answer 68

Reluctance (S)

Question 69

It is the reciprocal of permeability.

Answer 69

Permeance

Question 70

What is the formula for Reluctance?

Answer 70

S = length / (μo • μr • A) where A is the cross-section area of the conductor

Question 71

What is the relationship between the flux, mmf and reluctance.

Answer 71

Φ = NI/S

Question 72

What is the formula for Reluctance in series?

Answer 72

St = S1 + S2 + ... + Sn

Question 73

What is the formula for Reluctance in Parallel?

Answer 73

St = 1/ [ (1/S1) +(1/S2) + ... + (1/Sn) ]

Question 74

The heat due to hysteresis released per cycle per unit volume or iron is approximately computed using:?

Answer 74

Steinmetz Formula

Question 75

What is the General Formula for Hysteresis loss?

Answer 75

Pb = η * Bmax^n * f * V

Question 76

The formula for hysteresis loss per cycle per unit volume of iron is _________.

Answer 76

Wh = η * f * Bmax^1.6

Question 77

This is the emf induced in a wire by moving either the wire or the magnet so that flux cutting results (principle used in generator)

Answer 77

Dynamically Induced emf

Question 78

What is the formula for Dynamically Induced emf

Answer 78

E = BLvsinθ where v is the velocity of wire movement.

Question 79

This is the emf induced in a wire by changing the magnetic flux linking with the coil.

Answer 79

Statically Induced emf

Question 80

What is the formula for Statically Induced emf?

Answer 80

E=N * dθ/dt where N is the number of turns

Question 81

This is a kind of magnetic material that is least magnetic. It has a relative permeability equal to 1.

Answer 81

Non-magnetic

Question 82

This is a kind of magnetic material with relative permeability lesser than 1.

Answer 82

Diamagnetic

Question 83

What is an example of a diamagnetic material?

Answer 83

Copper

Question 84

It is a magnetic material with relative permeability slightly greater than 1

Answer 84

Paramagnetic

Question 85

Give an example of a paramagnetic material.

Answer 85

Aluminum

Question 86

It is the most magnetic of all magnetic materials, It can retain magnetism and is used to create magnets. It has relative permeability highly greater than 1

Answer 86

Ferromagnetic

Question 87

It is a magnetic material that does not absorb the magnetic field but repel it.

Answer 87

Diamagnetic

Question 88

It is the amount by which relative permeability differs from unity and it has no unit.

Answer 88

Susceptibilty (Xm)

Question 89

What is the formula for Susceptibility?

Answer 89

Xm = μr - 1

Question 90

1 A-t (Ampere-turn) = _____ Gilbert (Gb)

Answer 90

1.256

Question 91

1 oersted = ___ Gb/cm

Answer 91

1

Question 92

It is the dependence of the state of a system on its history.

Answer 92

Hysteresis

Question 93

A magnetic moment at which the resistance of a magnetic material changes in magnetization. It is equivalent to field intensity necessary to demagnetize a fully magnetized material.

Answer 93

Coercivity

Question 94

This is the ability of a material to retain magnetization.

Answer 94

Retentivity

Question 95

This is another word for residual magnetism.

Answer 95

Remanence