P7

Question 1

What are each end of the magnet called

Answer 1

Poles
North and south

Question 2

Where are magnetic feilds strongest

Answer 2

At the poles

Question 3

What happens when we bring two magnets close together

Answer 3

They exert a force on eachother
Like poles repel
Unlike poles attract
Non contact forces

Question 4

What is a permanent magnet

Answer 4

A magnet which produces its own magnetic field

Eg bar magnet

Question 5

What is an induced magnet

Answer 5

An object that become a magnet when it is placed in a magnetic field

Always causes force of attraction

Question 6

What are the magnetic materials

Answer 6

Iron steel cobalt nickel

Question 7

What is a magnetic field

Answer 7

A region around a magnet where a force acts on another magnet or magnetic material

Question 8

What happened if we place a magnetic material into a magnetic field

Answer 8

Experiences a force of attraction towards the magnet

Question 9

How can we find magnetic field

Answer 9

Using a magnetic compass
-place compass near north pole
-draw cross at north pole of the magnet
-move the compass so the South Pole is on the cross,draw another cross at north pole
-continue until we have plotted a magnetic field line
-join crosses with straight line and draw arrow on direction

Question 10

How do we know the earth has it’s own magnetic field

Answer 10

If we hold a compass away from any magnet then the needle always points in the north-south direction.

Question 11

What happens when a current flows through a conducting wire

Answer 11

A magnetic field is produced around the wire

Question 12

How can we increase magnetic feild strength produced by a solenoid

Answer 12

-increase current
-iron core
-increase turns of coils

Question 13

What happenes in a solenoid if we change the direction of the current

Answer 13

We change the direction of the magnetic field

Question 14

How can we figure out direction of current

Answer 14

Flemings right hand rule

Place our right hand so the thumb is in the direction of the current,now the fingers are pointing in the direction of the magnetic field

Question 15

What is a solenoid containing an iron core called

Answer 15

Electro magnet

Question 16

Why are electro magnets useful

Answer 16

-We can change the strength
-turn on or off

Question 17

What is the motor effect?

Answer 17

If you bring a current carrying wire near another magnetic field, the fields interact and a force is produced

Question 18

How do we calculate the size of force produced during Moter effect

Answer 18

F=BxIxL
Force (n)=
magnetic flux density (T) x current (A) x length (m)

Question 19

How do we determine direction of force during motor effect

Answer 19

Flemings left hand rule
Thumb=direction of force
First finger=direction of magnetic field
Second finger= direction of current

Question 20

What happens in the motor effect if the conductor is parallel to the magnetic field

Answer 20

It will not experience a force

Question 21

How does a motor continue spinning

Answer 21

For a motor to continue spinning A split ring communicator is used, this swaps the contacts of the motor every half turn therefore reversing the current

Question 22

When there is a current in a coil,the coil rotates continuously

Why?

Answer 22

-The coil in the magnetic field will experience a force when current flows
-The current will flow in opposite directions in the coil, so each side will experience in opposite force which allows it to turn
-Every half a turn, the rotating communicator swaps carbon brush, and the current is reversed
-This reverses the force, each side experiences, keeping it rotating

Question 23

What does switching the direction of the current do in an electric motor?

Answer 23

By switching the direction of the current, the split ring communicator, allows the motor to keep rotating in the same direction

Question 24

how can we use a permanent magnet to identify a permanent magnet,magnetic metal and regular metal

Answer 24

-permanent metal will attract magnetic material
-magnet would have no effect on regular metal
-magnet could only repel the permanent magnet

Question 25

how can a electromagnet be used to move magnetic materials

Answer 25

-by completing the circuit the electromagnet is turned on
-there is a current in the coil which produces a magnetic field around the coil
-move electromagnet towards the blocks
-the block is attracted to the electromagnet
-switching off the current switches off the electromagnet
-releasing the block

Question 26

how to find frequency

Answer 26

-use a stopwatch
-count the number of waves passing a point in a fixed time period
- divide the time by the number of waves to determine the time or one wave, T
-f = 1/T

Question 27

how to find wavelength

Answer 27

-use a camera to freeze the image
-use a metre rule to measure the distance between two
wavefronts
- count the number of waves between the wavefronts
-divide distance by the number of waves to determine λ

Question 28

The paper clip in Figure 2 is not a permanent magnet.
Explain what would happen if the paper clip was removed and brought close to the
south pole of the permanent magnet.

Answer 28

-paper clip will still experiannce a force of attracton towards the magnet
-because its become an induced magnet