Magnetism and Electromagnetism - Electromagnetism

Question 1

what does electric current in a conductor produce?

Answer 1

• a current travelling along a wire produces a circular magnetic field around the wire
• magnetic field direction can be determined using the right hand grip rule

Question 2

how is the motor effect used in d.c electric motors?

Answer 2

• current flows in the wire/coil.
• creating a magnetic field around the wire/coil.
• the magnetic field interacts with the field from the permanent magnet
• this produces a force on the wire/coil which moves the wire/coil
• a split-ring commutator changes the direction of the current every half turn as it spins, reversing the direction of the forces, allowing the coil to continue spinning

Question 3

how is the motor effect used in loudspeakers?

Answer 3

• an alternating current from the source passes though the coils in the speaker
• AC is constantly changing direction and magnitude
• current creates a magnetic field around the coil
• this field interacts with the magnetic field from the permanent magnets
• this creates a constantly changing force on the coil
• this causes the coil to vibrate in and out as the direction of the force changes, moving the cone
• the cone causes vibrations which we hear as sound waves.

Question 4

what is flemmings left hand rule?

Answer 4

• thumb: force
• First finger: magnetic Field
• seCond finger: Current

Question 5

how does the force on a current-carrying conductor in a magnetic field changes with the magnitude and direction of the field and current?

Answer 5

• if you increase the magnitude of the current through a wire or the size of the magnet being used, you increase the force on the wire
• if you change the direction of the current or reverse the poles of the magnet, you change the direction of the force on the wire