7 Electromagnetism 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

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)

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

4
Q

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

A

1- more turns

2- increase the current

5
Q

Draw the shape of a magnetic field around a coil.

A
6
Q

Draw the magnetic field around a solenoid.

A
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.

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.

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

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.

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

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

13
Q

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

A

Stronger magnetic field

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

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.