Electromagnetic induction - magnetic fields

Question 1

Which direction would the arrows be going near a south pole?

Answer 1

Towards

Question 2

Which direction would the arrows be going near a north pole?

Answer 2

Away

Question 3

Which direction does a dot show in a magnetic field diagram?

Answer 3

Coming out of the page

Question 4

Which direction does a cross show?

Answer 4

Going into the page

Question 5

Magnetic fields cause what?

Answer 5

Magnetic fields cause a moving charge to feel a force.

Question 6

What do moving charges produce?

Answer 6

Moving charges produce a magnetic field around itself.

Question 7

Explain the right hand grip rule.

Answer 7

• Thumb: showing the direction of CONVENTIONAL current.

- Fingers: showing the direction of the magnetic field

Question 8

How do you increase the strength of the magnetic field around a current carrying wire? (3 points)

Answer 8

• Increase the current
• Increases number of charges flowing
• Stronger magnetic field

Question 9

How does a coil of insulated wire with current produce a magnetic field?

Answer 9

• Current flows through the wire

- Using the right hand rule the magnetic field goes through the middle of the coil

Question 10

An example of a permanent magnet and a temporary magnet?

Answer 10

• Perm; bar magnet

- Temp; solenoid

Question 11

Magnetic Flux Density is…

Answer 11

… is the density of magnetic field lines in a given area (strength of a magnetic field).

Question 12

Letter and unit for Magnetic Flux Density

Answer 12

B, Tesla (T)

Question 13

Flux is…

Answer 13

… is a scalar measure of the magnetic field interacting with a surface area

Question 14

Letter and unit of Flux

Answer 14

Φ, Weber (Wb)

Question 15

Flux linkage is…

Answer 15

… is the flux interacting with multiple loops in a coil, rather than just one wire/surface

Question 16

Letter and unit for Flux Linkage

Answer 16

NΦ (N = number of loops), Weber-turns (Wb-turns)

Question 17

What is the equation used to link flux and magnetic flux density?

Answer 17

Φ = BA sinθ

Question 18

Fleming’s left hand rule

Answer 18

Follow FBI

• Thumb: direction of force
• Index: magnetic field direction
• Middle: direction of CONVENTIONAL current

Question 19

If the field lines and direction of current are parallel, is there a resultant force?

Answer 19

No, because sinθ would be sin(0) which is equal to 0.

Question 20

Derivation of r = p / BQ

Answer 20

• F = Bqv
• F = mv^2 / r
• Bqv = mv^2 / r (make them equal)
• Bq = mv / r (divide by v)
• Bq = p / r (p = mv)
• p / Bq = r (rearrange)

Question 21

If the velocity decreased of a moving charge through a magnetic field, what would happen to it’s turn radius?

Answer 21

• F = Bqv sinθ
• if v decreased and the centripetal acceleration didn’t change
• as F = Bqv sinθ is lower, F of F = mv^2 / r is lower
• r must have decreased so
• tighter turn radius of charge

Question 22

Derive F = BIl from F = Bqv

Answer 22

• F = Bqv
• F = BQv (I = Q/t)
• F = BItv (v = s/t)
• F = BIs (s = distance = length)
• F = BIl

Question 23

Equation for flux (fie)

Answer 23

flux = BA sin (theta)