6.3 Electromagnetism

Question 1

What is a magnetic field

Answer 1

A field surrounding a permanent or a current-carrying conductor in which magnetic objects experience a force

Question 2

How are magnetic fields created

Answer 2

A moving charge

Question 3

What does the arrow on a magnetic field line tell you

Answer 3

The direction in which a free North Pole would move - the arrow points from north to south

Question 4

What does it mean if magnetic field lines are parallel and equally spaced

Answer 4

Represents a uniform field

Question 5

How can you tell where the field is the strongest

Answer 5

When the magnetic field lines are closer

Question 6

What are the rules of repulsion and attraction of magnetic poles

Answer 6

Like poles repel and unlike poles attract

Question 7

What is the right hand grip rule

Answer 7

A way to determine the direction of the magnetic field

Question 8

What does the thumb represent in the right hand grip rule

Answer 8

The thumb point in the direction of the conventional current

Question 9

What do the fingers represent in the right hand grip rule

Answer 9

The direction of the field is given by the direction in which the fingers curl around the wire

Question 10

How does the magnetic field pattern of the solenoid change if the direction of the current is reversed

Answer 10

The direction of the field is reversed

Question 11

What happens when you place a current-carrying conductor in an external magnetic field

Answer 11

The two fields interact just like in the fields of two permanent magnets- they experience equal and opposite forces

Question 12

What is Flemings left hand rule

Answer 12

If fingers are positioned perpendicular to eachother, the thuMb will represent Motion, the First finger will represent Field and the seCond finger represents Current

Question 13

What does the magnitude of the force experienced by a wire in an external magnetic field depend on

Answer 13

Current, Length of wire in the field, sin θ (θ= angle between field and current direction), strength of field

Question 14

When’s the force on a current carrying wire in an external maximum and when is it zero

Answer 14

The force is maximum when the wire is perpendicular to the field and zero when parallel to the field

Question 15

State the equation for the force on a current carrying wire in an external field

Answer 15

F=BILsinθ (force= magnetic flux density x current x length of wire x sin(angle between field and current direction))

Question 16

State the equation for the force on a current carrying wire perpendicular to the field

Answer 16

F=BIL

Question 17

What are the units of magnetic flux density

Answer 17

Tesla (T)

Question 18

How is magnetic flux density defined

Answer 18

The strength of the field

Question 19

What are the SI units for magnetic flux density

Answer 19

Nm^-1A^-1

Question 20

Is magnetic flux density a vector or scalar quantity

Answer 20

Vector

Question 21

What happens when a charged particle moves in a magnetic field

Answer 21

The particle will experience a force

Question 22

How can you determine the direction of the force on a charged particle moving in a magnetic field

Answer 22

Fleming’s left hand rule

Question 23

why does the force on the beam of electrons in an electron gun with a visible screen is directed downwards

Answer 23

As the electrons enter the field, they experience a downwards force which always remains perpendicular to its velocity

Question 24

Describe the path of a beam of electrons travelling perpendicular to a magnetic field

Answer 24

Electrons travel in a circular path in the region of the field then keep moving in a straight line once out of the field

Question 25

why does the speed of the electrons remains unchanged when travelling perpendicular to a field

Answer 25

Because the force has no component in the direction of the motion

Question 26

State the equation for the force on a charged particle travelling perpendicular to a magnetic field

Answer 26

F=BQV (force= magnetic flux density x charge x speed of charged particle)

Question 27

What’s the expression for the radius of the circular path taken by charged particles moving perpendicular to a field

Answer 27

r=mv/BQ (radius= mass x velocity/ magnetic flux density x charge)