P7: THE MOTOR EFFECT + FLEMING'S LEFT HAND RULE

Question 1

What is the motor effect?

Answer 1

-when a wire carrying current is placed in a magnetic field, it experiences a force
-current must be perpendicular to the magnetic field

Question 2

-When current flows through a wire, the current creates a _________ ________ around the wire
-when the current-carrying wire is placed in a magnetic field, the magnetic field ________ with the magnetic field of the magnets
-this causes a _____ to act on the ______

Answer 2

-when current flows through a wire, the current creates a magnetic field around the wire
-when the current-carrying wire is placed in a magnetic field, the magnetic field interacts with the magnetic field of the magnets
-this causes a force to act on the wire

Question 3

How can the force acting on a wire be increased?

Answer 3

-increasing strength of magnet
-increasing the length of the wire inside the magnetic field
-increasing current through the wire

Question 4

What is the equation linking force. magnetic flux density, current and length of wire?

Answer 4

force (N) = magnetic flux density (T) x current (A) x length of wire (m) (F = BIl)

Question 5

What is Fleming’s left hand rule?

Answer 5

-the forefinger is lined up with magnetic field lines pointing from north to south
-the second finger is lined up with the current pointing from positive to negative
-the thumb shows the direction of the motor effect force on the conductor carrying the current

Question 6

What does Fleming’s left hand rule allow us to work out?

Answer 6

the direction of the force acting on the wire if we know the direction of current and magnetic field lines

Question 7

How does an electric motor work?

Answer 7

-the loop of wire has current flowing through it and is in a magnetic field so it experiences a force
-current flows in the opposite directions on each side of loop
-using Fleming’s left hand rule, the left hand side of the coil will move upwards
-the right hand side of the coil will move downwards
-so the coil will rotate in the clockwise direction
-the split-ring commutator reverses current every half-turn to keep the loop rotating in the same direction