ECE 30411 exm 3

The integral ∮ H · dS over a closed surface will always be zero

False

The integral ∮ B · dS over a closed surface will always be zero ->

True

The net force on a current loop in a uniform magnetic flux density field will be zero

True

At the Curie temperature the north and south poles of a bar magnet will change positions

False

For a ferromagnetic material, when all the magnetic domains are pointing in the direction of the external magnetic field, the slope of the H versus B curve will be zero

False

A diamagnetic material is repelled by a permanent magnet

True

A ferromagnetic material will retain a considerable amount of magnetization when removed from an external magnetic field

True

The force on a moving charge in a magnetic field does no work

True

Flux linkage is the number of turns per unit length of a coil

False

Two parallel coils with current flowing in opposite directions attract

False

Magnetic Field Intensity (H)

A/m (vector)

Magnetic Flux Density (B)

Wb/m² = T (vector)

Magnetic Flux (Φ)

Wb = V·s (scalar)

Magnetization (M)

A/m (vector)

Relative Permeability (μr)

dimensionless (scalar)

Magnetic Dipole Moment (m)

A·m² (vector)

Bound current

Current associated with electrons in orbit and electron spin in materials (not free current in wires)

The Earth’s magnetic field has flipped directions in the past

True

If a bar magnet is broken in half each piece will have both a north pole and a south pole.

False

A paramagnetic material is repelled by a permanent magnet

False

At the Curie temperature a ferromagnetic material becomes demagnetized

True

For a ferromagnetic material, when all the magnetic domains are pointing in the direction of the external magnetic field, the slope of the B versus H curve will be zero

False

Two parallel wires carrying current in the same direction will attract each other

True

∮ H · dl is always zero

False

A diamagnetic material is repelled by a magnet

True

A paramagnetic material is repelled by a magnet

False

When the magnetization saturates in a ferromagnetic material the magnetic flux density increases at a rate of μ₀ with further increase in applied magnetic field intensity

True

Dropping a magnet can demagnetize it

True

When two different materials are rubbed together, one becomes positively charged and one becomes negatively charged. This happens

because of the chemical potential difference between the two materials

Electric Field Intensity (E)

N/c or v/m (vector)

Electric flux density (d)

c / m² (vector)

Electric flux (Ψ)

C (scalar)

In cylindrical coordinates, a_ρ is normal to the surface ρ = 3 m

True

When producing static electricity by rubbing two different materials together, the charge is caused by friction

False

The total electric flux emerging from a closed surface is always zero

False

-a_z × a_ρ = a_φ

False

Electric Field Intensity is force per unit charge

True

Capacitance (more fundamental than Farad)

C/V (Scalar)

Electrical potential (more fundamental than Volt)

J/C (Scalar)

Polarization (P)

C/m^2 (Vector)

Dielectric constant (εr)

unitless (Scalar)

Electric dipole moment

C·m (Vector)

Resistivity

Ω·m (Scalar)

Volume current density

A/m^2 (Vector)

Electric Susceptibility (χₑ)

dimensionless (scalar)

Electric field intensities are tangent to equipotential surfaces.

False

For static fields ∫ E · dl is independent of the path

True

When a current is flowing in a conductor like copper the drift velocity is on the order of 10^-7 m/s

True

Free charge is charge tied up in an electric dipole

False

The value of the potential at a point in space is arbitrary. It is only the difference in potential between two points that has a unique value

True

In words, describe the shape of the equipotential surfaces around a point charge at the origin

spheres centered at the origin

If ∮ H · dl = 0 then H is zero everywhere

False

The ∮ H · dS is always zero

False

A particle is moving in a region that has a uniform electric field intensity and a uniform magnetic flux density. The force on the particle due to the electric field intensity is parallel to the electric field intensity and the force on the particle due to the magnetic flux density is perpendicular to the magnetic flux density

True

The ∮ M · dS is always zero

False

Inside a conductor (electrostatic equilibrium)

E = 0
V = constant
Charge is on surface

Battery connected

V = constant

Battery removed

Q = constant

The velocity of an electromagnetic wave is always the same irrespective of the material in which the wave is propagating

False

For a proposing electromagnetic wave, the electric field intensity is the direction of propagation

False

The earth’s magnetic field has flipped direction in the past

True

What does the electric potential difference VA - VB, represent?

The amount of work to move 1C of charge from point B to point A

Electromagnetic waves travel faster in dielectrics than is free space

false

Over a closed path ∮ E · dl is always zero

False

The velocity of an electromagnetic wave is always the same irrespective of the material in which the wave is propagating

False