13 Electromagnetism- 4th Form Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Describe the shape of the magnetic field around a wire

A

Circular field shape

field lines getting futher apart- field getting weaker as you move away from the wire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do you determine the direction of a magnetic field around a wire?

A

Use the right hand grip rule

Thumb- direction of current

Fingers- wrap in direction of magnetic field (clock wise or anti-clockwise)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How would you construct a simple electromagnet?

A

1) wrap a wire around an iron nail
2) connect a cell across the wire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What can be done to increase the magnetic field around a solenoid?

A

1- more turns

2- increase the current

3- add an iron core

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Draw the shape of a magnetic field around a coil.

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Draw the magnetic field around a solenoid.

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens to the magnetic field around a wire if more wires are added side by side- How can you tell from the image that the magnetic field is stronger?

A

More wire- stronger field

The closer the magnetic field lines the stronger the field.

iron filing will line up more easily and more closely together in a stronger magnetic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

If a vertical wire has the current upward in the wire, work out the direction of the magnetic field using your Right Hand Grip Rule

A

Thumb- up and in direction of current

Finger wrap in direction of magnetic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How would you demonstrate the direction of the magnetic field around a single wire?

A

Place compasses around the wire

The compass will point in the direction of the magnetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens to the direction of the magnetic field around a magnet if the direction of the current it reversed?

A

The direction of the magnetic field is reversed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do we use dot and crosses to represent the direction of a mangetic field or current?

A

dot means out of the page

cross means into the page

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do you use the right hand grip rule to work out which end of a solenoid is the north end?

A

Fingers- wrap your fingers in the direction of the current

Thumb- will point to the North end of the solenoid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens to the magnetic field around a solenoid if you add an iron core (magnetically soft)

A

Stronger magnetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is iron a better core to use in an electromagnet than steel?

A

Iron is magnetically soft- the domains in iron line up easily - it can magnetise and demagentise easily

Steel is magnetically hard- the domains do not line up easily- it cannot magnetise easily and it can be used to make permananet magnets becaouse it also does not easily demagnetise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Electromagets are used in electric bells.

  • When the button is pushed, a current flows in the electromagnet -This creates a magnetic field around the electromagnet
  • The electromagnet attracts the soft iron armature which moves to the right
  • This causes the hammer to hit the bell.

What happens next?

A

The moment the iron armature moves to the right this creates a _break in the circuit- t_he circuit is no longer complete.

The current drops to zero and the magnetic field around the electromagnet disappears.

The iron armature is no longer attracted and springs back to the left

The armature completes the circuit again and the whole cycle repeats alowing the bell to repeatedly sound.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Define a magnetic field

A

A region of space where a magnetic material experiences a force

17
Q

How can a magnetic field be induced?

A

Hold a magnet near an iron nail. The domains in the iron nail align - there is now an induced magnetic field around the nail