Investigating flux density Flashcards Preview

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Flashcards in Investigating flux density Deck (13):
1

Describe the set up of the equipment?

  • U magnet on zeroed top pan balance
  • thick, current carrying copper wire place perpendicular to magnetic through the centre
  • connected to variable resistor, and ammeter to measure current

 

 

2

How is the current varied>

  • variable resistor

3

When is the balance zeroed?

  • when thee is no current through the wire
  • so that the mass reading is due to the electromagneti cforce only

 

 

4

What is recorded? What is the independant and dependant variable?

  • independant 
    • current
  • dependant
    • mass reading

5

What is the procedure?

  • balance zeroed then current switched on
  • current and balance reading are recorded
  • current increase
    • reading taken for at least six reading
    • repeats

 

6

How is a uniform field created?>

  • magnets have their poles on their faces and are fixed to a stell yoke, creating a magnetic field
  • important to check the magnets attract to ensure a norht pole faces a south pole

 

 

7

What must the structure of the wire be?

  • thick and rigid 
  • supported horizontally

8

How are the readings converted?>

  • converted to force using F = mg 

 

9

How can magnetic flux density be worked out?

  • graph of F against I
  • because F = BIL, BI = gradient
  • divide by lengtrh to get a vlue for B

 

 

10

What is an alternative procedure for this experiment?

  • vary length of wire perpendicular to the magnetic field by using different size hoops 
    • adding additional yokes
  • yoy could keep current and wire length the same and instread vary the magnetic field by changing the strength of magnets

 

 

11

Why is a sensitive top pan balance useD?

  • small forces
  • sensitive to measure the force

 

12

How does this relate to Newton's third law?

  • the magnetic force experienced by the wire will be equal in size, but in the opposite direction to the force on the permanant U-shaped magnetis

 

 

13

What are the safety considerations?

  • in order to produce measurable magnetic forces, relatively large currents have to be used
    • causes wire to heat up
    • so turns circuit off between readings
    • reduce degree of heating
  • rheostat (electrical instrument used tocontrol current by varying resistance) needs to have a large power instrument to cope with the large current and heat produced