Unit 4 - Lesson 7: The Motor Effect

Question 1

What kind of field is produced around a current carrying wire?

Answer 1

A magnetic field.

Question 2

If you put a current carrying wire inside a magnetic field, what happens?

Answer 2

The two fields overlap.

Question 3

If there are more field lines in an area, is the magnetism stronger or weaker?

Answer 3

Stronger. This exerts a force on the wire. It moves. This will happen to any conductive material carrying a current in a magnetic field.

Question 4

What does the strength of the force depend on?

Answer 4

Depends on the magnitude and direction of the magnetic field and/or current.

Question 5

How can we demonstrate that the strength of the magnetic force depends on the magnitude and direction of the magnetic field and/or current?

Answer 5

We can demonstrate this using a horseshoe magnet. When a current is applied, the bar will roll along the rails. Increasing current (by increasing voltage supply) makes the bar roll faster. Stronger magnets make a stronger magnetic field. The ball will roll faster due to a greater force.

https://i.pinimg.com/736x/b3/99/90/b3999008ba664595b42df4411e77ad0c.jpg

Question 6

Draw a field around a current-carrying wire.

Answer 6

https://i.pinimg.com/736x/ea/61/d4/ea61d45bcb4e4318324e4b6eeb4bbe23.jpg

Question 7

Draw a uniform field between permanent magnets.

Answer 7

https://i.pinimg.com/736x/00/79/10/00791031416c1713362804607fe07893.jpg

Question 8

Draw a deviated magnetic field.

Answer 8

https://i.pinimg.com/736x/47/78/9e/47789edd053dd078bdfd13b1f147c01e.jpg

Question 9

What rule did Fleming create to be able to tell the direction of the force (where the object moves), magnetic field and current?

Answer 9

Flemings left hand rule. Move your hand in this shape:

https://i.pinimg.com/736x/a1/49/79/a14979fa422bc5720c0c341e517fac9e.jpg

Imagine you know the direction of the magnetic field (it’s always from north to south). Position your hand so your fore finger points in that direction. Your thumb will then tell you the direction of the force (where the wire will move). Therefore, the further the distance from the wire, the lower the magnitude of the field (it’ll be weaker).

Question 10

The further the distance from the wire, the lower the magnitude of the field (it’ll be weaker). True or false?

Answer 10

True.

Question 11

The exam may trick you by not providing the direction of the current. What way do magnetic field lines go around a current-carrying wire?

Answer 11

Anticlockwise.