Electromagnetism level 7-9

Question 1

Explain how field lines relate to the strength of the magnetic field

Answer 1

The strength of the magnetic field is shown by how close together the field lines are. The closer together they are the greater the strength of the magnet.

Question 2

Explain how induced magnetism occurs

Answer 2

Magnetic materials contain domains. Domains are like small magnets inside the material. When far away from magnets the domains are randomly aligned and of the same size.

If the metal is placed near to a magnetic field the domains in line with the field lines grow larger. This give the magnet an overall magnetic field in the same direction as the magnet it is next to.

Question 3

Explain how to determine the direction of the magnetic field in a solenoid if you know the direction of the current

Answer 3

Use the right hand screw rule. Using your right hand, curl your fingers in the direction the current is moving through the solenoid. Your thumb is pointing in the direction of the north pole

Question 4

What is the purpose of the iron core in an electromagnet

Answer 4

The iron core magnifies the strenght of the magneid field by concentrating all of the field lines in one place

Question 5

Explain how an electric motor works

Answer 5

In an electric motor current flows through a coil which is inside a magnetic field

When the current flows through one side of the coil, it will generate an upwards or downwards force on that side of the coil

As the current is travelling in the other direction through the other side of the coil, it will feel a force in the opposite direction.

This creates a moment that causes the motor to turn

Every half turn the split ring comutator changes the direction of the current. This means that the force on one side is always down and the force on the other side is alwys upwared, meaning the motor keeps spinning in the same direction.