Magnetic fields

Question 1

Cutting magnets in half

Answer 1

• poles cannot be isolated; a magnet cannot be broken to get a separate north and south pole. Instead, it creates 2 magnets each with a north and south pole.

Question 2

Magnetic Domains

Answer 2

• in order for a material with domains to become magnetic, the domains have to be aligned by an external magnetic field
• if enough of a materials domains become aligned, the material forms a magnetic dipole and becomes a permanent magnet

Question 3

Magnetic field lines

Answer 3

• point from north to south
• a compass would align with these lines
• a horseshoe magnet is just a bent bar magnet. the rules still apply

Question 4

B-field

Answer 4

B - magnetic field strength [T]

Question 5

Right hand rule #1

Answer 5

• thumb points in direction of the current
• fingers point in direction of the field lines

Question 6

Drawing in 3D

Answer 6

Conventions to help us out:
Into the paper: x
out of the paper: O

Question 7

Looped wire

Answer 7

A wire in a loop has a stronger magnetic field inside the loop than outside

Question 8

Right hand rule #2

Answer 8

• thumb points in direction of the current
• fingers point in direction of the field lines
• palm points in direction of the force

Question 9

Designing a motor

Answer 9

when electric current is passed through a magnetic field, you get motion

Question 10

Motors vs. generators

Answer 10

Electric motors convert electricity to motion.

Electric generators convert motion to electricity.

Question 11

Ampere

Answer 11

One ampere is defined as the current that would cause a force of 2 x 10-7N per meter between 2 long parallel conductors separated by 1m in a vacuum

Question 12

Fields

Answer 12

g = F/m [N]/[kg]
E = F/q [N]/[C]

B = F/I [N]/[A] = [T]

Question 13

Magnetic flux

Answer 13

• depends on how perpendicular the current is in relation to the field direction
  Max flux: vertical
  Less flux: narrow
  No flux: horizontal

Question 14

Magnetic field strength

Answer 14

B = F/ILsin0
F - magnetic force [N]
I - current [A]
L - length of wire in field
sin0 - angle between field and current

**L=vt
**I = q/t

• the force on the wire is proportional to the charge moving perpendicular to the field
• because of these, the perpendicular component must be used in calculations

Question 15

Quantized electric charge

Answer 15

every measured value of electric charge is an integral multiple of a certain fundamental quantity of charge