Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level Physics Year 2 > Magnetic Fields > Flashcards

Magnetic Fields Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What happens when a current-carrying wire goes in a magnetic field ?

A

the current-carrying wire will experience a force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

State the condition for F = BIL

A
  • the direction of the force acting in a current-carrying wire is PERPENDICULAR to a magnetic field
  • the current flow in wire must be perpendicular to a magnetic field
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Fleming’s Left hand rule ?

A

First finger =Field
Second finger = current
Thumb = force (motion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What happens when charged particle moves through a magnetic field ?

A

the charged particle will experience a force
- current I = Q/t
- distance L = vt
F = BQv

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens when charged particle moves perpendicular into a magnetic field ?

A

it will flow a circular motion

  • the force is always towards the centre of the circle
  • the direction of the particle is the Second finger (normally current)
  • if negative charge then point finger in the opposite direction to its motion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is the radius and frequency of the circular motion of the charged particle affected ?

A

RADIUS r = mv/BQ
-mass or velocity increase = radius decrease (less deflect)
- magnetic field/charge increase = radius increase
FREQUENCY f=BQ/2πm
- frequency of rotations is independent of its velocity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is Magnetic Flux density (B) ?

A

force acting on one metre of wire carrying a current on one amp

  • is a vector
  • measured in teslas (T)
  • known as magnetic field strength
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is one Tesla equal to ?

A

equal to one newton per amp per metre (1T = 1N/Am)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the right hand rule used for ?

A

to work out the direction of a magnetic field around a current -carrying wire
- thumb = current
= fingers = magnetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Representation of magnetic field on magnet and paper ?

A

MAGNET
- the magnetic field lines go from NORTH to SOUTH
- NORTH = anticlockwise current (N)
- SOUTH = clockwise current (S)
PAPER
- the magnetic field goes INTO paper when a +
- the magnetic field goes OUT paper when a •

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How particles accelerators such as CYCLOTRONS make use of the force that acts on charged particles moving perpendicular to a magnetic field ?

A

HOW

  • two electrodes
  • charged particle start in centre - circular motion out
  • particle accelerates between electrodes so potential difference create and particle increase speed
  • spend equal time in each electrode as frequency is independent of velocity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Uses of CYCLOTRONS ?

A

USES

  • Medicine
  • Provide radioactive traces
  • High energy beams for use in radiotherapy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is Magnetic Flux (Φ) ?

A

The magnetic flux passing through an area is given by the magnetic flux density multiplied by the area
Φ = BA
- Measured in Wb (Weber’s)
- the number of magnetic field lines passing through the area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

When is an E.M.F induced across a conductor ?

A

when the conductor moving through the magnetic field or a conductor inside a changing magnetic field
- if the conductor in a circuit then a current will flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is Magnetic Flux linkage (NΦ) ?

A

NΦ = BAN
N - number of turns on the coil cutting the wire
- Measured in Wb (Weber’s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does the Rate of change in Flux linkage tell you ?

A

It tell you how strong the electromotive force (EMF) will be in volts
- A CHANGE IN FLUX LINKAGE OF ONE WEBER PER SECOND WILL INDUCE AN EMF OF 1 VOLT IN A LOOP OF WIRE

17
Q

How to calculate either the Magnetic Flux or Flux linkage of a rectangle coil when the coil is not normal to B ?

A

1) Φ = BACOSѲ

2) NΦ = BANCOSѲ

18
Q

What is the Radius and frequency equation in magnetic field circular motion ?

A 
r = mv/BQ
f = BQ/2πm
19
Q

What is Faraday’s Law ?

A

The induced EMF = the rate of change of Flux linkage in a conductor
E = NΔΦ/Δt
- Measured in Volts (V)
- Need to know GRAPHS for Φ/t and E/t

20
Q

What is Lenz’s Law ?

A

The DIRECTION of the induced EMF is such that it will try to oppose the change of flux that is producing it
E = -(NΔΦ/Δt)
- agrees with the conservation of energy - they energy used to pull a conductor though a magnetic field, against the resistance caused by magnetic attraction, is what produces the induced current

21
Q

What happens when you drop a magnetic through a solenoid ? - Lenz’s Law

A

1) north and north end meet so repulsion - A

22
Q

What happen if no current is induced in circuit ?

A
  • no current = no magnetic field
  • but still EMF induced
  • fall at acceleration = g
23
Q

How is an EMF induced in a rotating coil ?

A
  • rotating caused alternating EMF is induced
    E = BANwSINwt
  • graph is E/t - sin graph - EMF is greatest when coil is parallel to Magnetic field (NΦ - Fluxage linkage= 0)
24
Q

What is Alternating Current ?

A

Changing direction with time

25
Q

How to operate an Oscilloscope ?

A

It displays voltage

1) Alternative Display
- y-gain = 2v per division
- time base = 1ms per division
- time basee off - straight line vertical
2) Direct Display
- time base on - straight line horizontal
- time base off - dot

26
Q

Who to calculate Time period, Peak Voltage and Peak-Peak Voltage from graph ?

A

1) Time period - one complete oscillation
2) Peak Voltage = Vo - amplitude
3) Peak-Peak Voltage = Vpp = whole vertical

27
Q

How to calculate ‘root mean square current and potential differences ?

A 
Vrsm = Vo/√2 (main electricity - 230v)
Irsm = Io/√2
Prms = Po/2 or 
Po = Vo x Io
28
Q

What is a Transformer and the shape of it ?

A

a device that makes use of electromagnetic induction to change the size of the Voltage for an alternating current
- Its a laminated iron core with a magnetic field around it and Primary and Secondary coil around

29
Q

How to calculate the number of turns on coils or voltage across coils ?

A

Ns/Np = Vs/Vp

30
Q

Who does a step-up and step-down transformer work ?

A

STEP-UP TRANSFORMER - increase voltage ( reduce power loss P=VI)
- having more coils turns (N) on Secondary coil
STEP-DOWN TRANSFORMER - decrease voltage
- having more coils turns (N) on Primary coil

31
Q

What causes Energy loss in transformers and how to reduce them ?

A

1) EDDY CURRENT (heat lost) - Laminating core so current can’t flow
2) Electrical resistance - Thick copper (low r)
3) magnetism/de-magnetism core - SOFT IRON
4) Air gaps/impurities - high quality iron

32
Q

How to calculate the efficiency of a transformer ?

A 
Power = V x I 
- POWER IN = POWER OUT 
- IpVp = IsVs
EFFICIENCY = IsVs/IpVp
- energy lost - E = Pt
33
Q

How is electrical power is transmitted in the National Grid ?

A

Power station -> Step-up -> Pylogens -> Step-down -> House (230V)
- Transformers step-up = high voltage = low current = LOW ENERGY LOSSES

A-level Physics Year 2 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions