Electricity And Magnetism

Question 1

We define Electric current (I) as the rate of flow of net charges through a selected area in a unit of time

Answer 1

I = Q / t

Question 2

Electric current (I) is: a scalar or vector

Answer 2

scalar

Question 3

SI unit (measurement) of Electric current (I) :

Answer 3

ampere

Question 4

One ampere =

Answer 4

one coulomb per second

Question 5

Electrons rapidly collide with ions, even with the absence of the Electric Field (E).

Answer 5

In metals and other conductors

Question 6

In a conductor, an electron with a charge (q) acquiring extra kinetic energy due to work of the external force (F) of the electric field (E).

Answer 6

F = qE

Question 7

Voltage (V) between two points is defined as electric field (E) times the displacement ( lower case L ) between these two points.

Answer 7

V = E l

Question 8

Voltage is a: scalar or vector

Answer 8

Scalar

Question 9

SI unit (measurement) of voltage:

Answer 9

Volt

Question 10

Volt =

Answer 10

Walt over ampere (W/A)

Question 11

Batteries are common sources of:

Answer 11

fixed voltage &

relatively constant voltage.

Question 12

Power outlets are sources of:

Answer 12

oscillating voltage

Question 13

The proportionality of the electric current inside a conductor to the electric field is expressed in Ohm’s Law:

Answer 13

V = I R

Question 14

V = I R

Answer 14

(V) voltage applied to the piece of conductor (such as wire)
(I) electric current through the conductor
(R) electric resistance of the piece of material

Question 15

Electric resistance (R) - being a ratio of two scalars- is :

Answer 15

scalar

Question 16

The SI unit (measurement) of Electric resistance (R)

Answer 16

Ohm

Question 17

Ohm =

Answer 17

Volt over ampere (V/A)

Question 18

Kirchoff’s laws for electric circuits:

Answer 18

Loop rule: Voltage drop across a closed circuit loop is zero. ( V - IR = 0 )
Branch rule: Net current into a single circuit branch is zero. ( I = I1 + I2 )

Question 19

Using Kirchoff’s law and Ohm’s law it is easy to derive total resistance of a circuit for resistors in series and resistors in parallel.

Answer 19

( R = R1 + R2 + R3 ) resistors in series

1/R = 1/R1 + 1/R2 + 1/R3

Question 20

In many conductors, the current is proportional to:

Answer 20

The applied electric field (E) (and voltage)

Question 21

A simple example of an electric current is:

Answer 21

an incandescent lamp

Question 22

Measures resistance to the flow of electricity:

Answer 22

Ohm

Question 23

Voltage source that converts chemical energy to electrical energy:

Answer 23

Battery

Question 24

The unit and symbol for current

Answer 24

Ampere, I

Question 25

Something that allows electricity to pass through it:

Answer 25

Electrical conductor

Question 26

Magnets exert magnet force on:

Answer 26

Iron objects

Question 27

Magnetic forces originate from:

Answer 27

moving electric charges

Question 28

Elementary particles like electrons:

Answer 28

behave like little magnets

Question 29

Prime examples of usefulness of magnetic force:

Answer 29

Electric power generators | Electric motors

Question 30

Strong magnetic fields are used in:

Answer 30

MRI's | microwave ovens

Question 31

Earths magnetic field enabled:

Answer 31

The compass. (the needle always aligns itself with the magnetic field lines)

Question 32

Magnetic field lines:

Answer 32

don't originate in a single point.

Question 33

The connection between electric and magnetic forces was first discovered by:

Answer 33

Oersted in 1819.

Question 34

Found that moving a magnet near a conducting loop induces electric current and likewise, changing current inside a conducting loop will induce electric current in a nearby conducting electic loop.

Answer 34

Faraday

Question 35

Magnetic field strength (B) is a: scalar or vector

Answer 35

vector

Question 36

SI unit (measurement) of magnetic field strength (B):

Answer 36

(N/Am) Newton per ampere meter

Question 37

(N/Am) =

Answer 37

(T) Tesla

Question 38

The magnetic force points in the direction perpendicular to the plane that is defined by:

Answer 38

the velocity vector and the magnetic field vector.

Question 39

The magnitude of the Lorentz force on a single particle where (q) is the charge of the particle, (v perpendicular) is the component of the particles velocity perpendicular to B, and (B) is the magnetic field strength.

Answer 39

F = q v perpendicular B

Question 40

Lorentz force on a wire: (I) current through the wire (L) length of wire (B) magnetic field

Answer 40

F = I L B

Question 41

Paramagnetic materials that increase the magnetic field less than .1%

Answer 41

Uranium and platinum

Question 42

- Diamagnetic materials | - decrease the magnetic field less than .1%

Answer 42

Bismuth, mercury, silver

Question 43

will align their electron loops with each other, even when no external magnetic field is present

Answer 43

ferromagnetic | ex: iron cobalt and nickel

Question 44

Amperes law for a long straight wire says the magnitude of the magnetic field strength produced by an infinitely long wire with current (I) inside is:

Answer 44

B = h I / r (r) distance from the wire (h) = 2x10^-7Tm/A (I) current in wire.

Question 45

AC electric motors create:

Answer 45

a rotating magnetic field

Question 46

If a person winds a coil of wire around a steel rod, and then passes an electric current through the wire, then:

Answer 46

the steel rod becomes an electromagnet

Question 47

magnetic fields are generated by:

Answer 47

electrons at rest, permanent magnets, moving charges

Question 48

two wires with electric currents running parallel to each other experience:

Answer 48

a mutual attraction

Question 49

two wires running antiparallel to each other experience:

Answer 49

a mutual repulsion

Question 50

the force on a moving charge in the presence of a magnetic field is always

Answer 50

perpendicular to both the charges velocity and the magnetic field

Question 51

the force on a moving charge in the presence of a magnetic field is always proportional to:

Answer 51

the velocity of the charge

Question 52

the force on a moving charge parallel to a magnetic field is always

Answer 52

0

Question 53

the force on a charge (q) moving with velocity (v) perpendicular to a magnetic field (B) is given by:

Answer 53

F = q v = B

Question 54

two kinds of the same magnetic pole

Answer 54

repel each other

Question 55

two kinds of the opposite magnetic pole

Answer 55

attract each other