Magnetic Fields

Question 1

5 characteristics of magnetic fields

Answer 1

1. Field lines never cross
2. Relative strength determined by the density of the lines
3. Lines run perpendicular to the metal surface they emanate from
4. Direction of lines is the direction of force acting on small north pole at that point
5. Lines run out of North pole into South pole

Question 2

What happens when current passes through solenoid?

Answer 2

A magnetic field is produced

Question 3

Compare RHGR and RHCR

Answer 3

RHGR: thumb = direction of current, fingers = direction of field lines
RHCR: fingers = direction of current flow, thumb = points in direction of north pole

Question 4

Define uniform circular motion

Answer 4

Refers to the motion of object that follows a perfectly circular path while the speed remains constant

Question 5

What is the key force acting in UCM?

Answer 5

Centripetal force (and acceleration) which acts towards the centre (unless object is subjected to centripetal force, it will not perform UCM)

Question 6

What does centripetal force do?

Answer 6

It causes a moving object to continually change direction towards the centre

Question 7

Where does centripetal force come from? (2 examples)

Answer 7

It is not a new force and for ball whirled in circle on string = tension force, car around corner = frictional force

Question 8

What provides the centripetal force for charged particles and what will happen if it is removed?

Answer 8

It is provided by the magnetic field when the charged particle is moving within it, and when the B-field is removed, object will fly off at a tangent