6 c) electromagnetism

Question 1

6.5 understand that an electric current in a conductor produces a magnetic field around it

Answer 1

When a current flows through a wire a magnetic field is created around the wire. This phenomenon is called electromagnetism. The field around the wire is quite weak and circular in shape. The direction of the magnetic field depends up the direction of the current and can be found using the flemmings’s left hand rule

Question 2

6.6 understand that a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers

Answer 2

As current passes around the loop of wire, one side of it will experience a force pushing it upwards. The other side will feel a force pushing it downwards, so the loop will rotate. This is used to produce movements in machines, cars etc.

Question 3

6.7 use the left hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field

Answer 3

http://www.shawonnotes.com/IGCSE_Physics/physics_images/left-hand-rule.jpg

The left hand rules shows the direction of force, magnetic field and current when a wire carries a current perpendicularly to a magnetic field.
The pointing finger points the magnetic field from North to South
The middle finger points the direction of current.
The thumb shows the resulting force.

Question 4

6.8 describe how the force on a current-carrying conductor in a magnetic field increases with the strength of the field and with the current.

Answer 4

Ways to increase the force produced in motors:

• Increase the number of turns or loops of wire
• Increase the strength of magnetic field
• Increase the current flowing through the loop of wire