Unit 11 - Magnetic Forces and Fields

Question 1

Magnetic fields occurs when

Answer 1

Objects interact in which there is a charge in motion

Question 2

What does the magitude of the magnetic force between two objects depend on

Answer 2

How much charge is in how much motion in each of the two objects and how far apart they are

Question 3

What is the equation for magnetic force

DEFINE thE TERMS

Answer 3

F = qvB
F = qvBsintheta 

q = charge 
v = velocity 
B = magnetic field strength 
theta = angle between velocity vector and the magnetic field vector

Question 4

Direction of the force can be found through the

Answer 4

RIGHT HAND SLAP RULE

Question 5

what is the right hand slap rule

Answer 5

Right hand out, palm up

from palm up = direction of force
middle finger points in direction of field
thumb - velocity

Question 6

What equation would allow you to find the force acting on a wire carrying current I in a magnetic field

Answer 6

F = BILsin theta

F = force 
B = magnetic field strength 
I = current 
L = length 
Theta = angle between moving current magnetic field vector

Question 7

What is the the cross product

Answer 7

a x b = mod A X mod B X sintheta n

Where n is a vector perpendicular to both a and b

Question 8

What is a magnetic field

Answer 8

A picture that we use to describe how magnetic fire i distributed in the space around and within something magnetic

Question 9

What is the unit of magnetic field strength

Answer 9

Tesla

How much force is applied to a moving charge due to the field

Question 10

Where do magnetic fields occur

Answer 10

Whenever there is a charge in motion as more charge is put in motion the strength of the magnetic field increases

Question 11

What is amperes law for magnetic field strength

Answer 11

B = Uo.I / 2pir

Uo - constant as perm of free space

Question 12

What is the constant of perm of free space

Answer 12

4pi X 10^-7

Question 13

What is the right hand grip rule, why may it be used

Answer 13

Used to determine the direction of both current and magnetic field strength

Fingers are direction of magnetic field strength (imagine arrows on the tips of the distal phalanges)

Thumb pointing up is the direction of the current

Question 14

What is the magnetic flux

Answer 14

Is measurement of the total magnetic ield that passes throguh an area

E.g. take field line drawing - each of the field lines contributes to the total magnetic flux

Question 15

What is the equation to calculate magnetic flux

Answer 15

o/ = BAcos theta

Where o/ = flux - units of Weber (wb)
B = magnetic field vector
A = area
theta = angle betwen the normal to the surface and the magnetic field vector

Question 16

what is magnetic flux density AKA

Answer 16

Magnetic flux per area

Question 17

What is electromagnetic induction

Answer 17

Process by which a current can be induced to flow due to a changing magnetic field

Question 18

What is Faradats law

Answer 18

A law that relates the rate of change of magnetic flux through a loop to the electromotice force (E) induced in the loop

Question 19

Electromotive force (E) =

Answer 19

Change in magnetic flux / Change in time

do/
___
dt

Question 20

What is Lenzs law

Answer 20

Tells us that current will be in the oppposite direction which opposes the change in flux that produced it

Question 21

Any magnetic field produced by an induced current will be in …

Answer 21

The opposite direction

Question 22

Give the equation relating to the Faraday Lenz Law

Answer 22

E = -NDΦ/dt

E = electromotive force
Φ = magnetic flux 
t = time 
N = number of turns in the wire coil