Magnetism And Electromagnetic- paper 2

Question 1

What is a magnetic field and how do you show a magnetic field?

Answer 1

.region where other magnets or magnetic materials experience a force
1)You can show a magnetic field=drawing magnetic field lines, lines always go from north to south
2)closer together the lines are, the stronger the magnetic field.further away from magnet you get, the weaker field is.

Question 2

Forces between a magnet and magnetic material is…?
What happens when the poles of two magnets are put together, what is this called?

Answer 2

1)force between magnet and a magnetic material=attractive, no matter the pole.
2)two poles magnet near each other=force attractive or repulsive.
.Two poles that are the same=repel. Two unlike poles=attract

Question 3

How do Compasses Show the Directions of Magnetic Fields? 2
What does it mean when the compass points north and why?

Answer 3

1)compass tiny bar magnet. north pole magnet attracted to South Pole magnet it is near.
2)compass points direction of magnetic field it is in

1)not near a magnet, compasses always point north.
2)Earth generates own magnetic field, core Earth magnetic.

Question 4

What are Permanent or Induced magnets properties?

Answer 4

1)Permanent magnets=produce their own magnetic field. attractive force
2)Induced magnets=magnetic materials turn into magnet when in a magnetic field. attractive force
If take away magnetic field, induced magnets lose their magnetism stop producing magnetic field.

Question 5

what happens when a current move through a wire?

Answer 5

1)current flows through a wire, magnetic field is created around the wire.
2) Changing the direction current changes the direction magnetic field

Question 6

What is the right hand thumb rule?

Answer 6

.right hand, thumb in the direction of current and curl your fingers.
.direction fingers is the direction of the field.

Question 7

How can you increase the strength of the magnetic field in a wire?

Answer 7

.wrapping wire into a coil=solenoid.

Question 8

Why does wrapping a wire in solenoid increase the magnetic field? 2
What is the magnetic field inside a solenoid like?

Answer 8

1)results lots of field lines pointing in same direction very close= stronger the field is.

3)magnetic field inside solenoid=strong and uniform (same strength direction every point in region).

Question 9

What is the magnetic field like outside the bar magnet?

Answer 9

.Outside the coil, magnetic field is just like the one round a bar magnet.

Question 10

How to increase the strength of a solenoid?

Answer 10

.increase the field strength of the solenoid=block of iron centre of the coil.
iron core= induced magnet whenever current is flowing.

Question 11

What is a electromagnetic magnet?

Answer 11

-when you stop current, magnetic field disappears.
-solenoid with an iron core (magnetic field can be turned on and off with an electric current)

Question 12

Why are electromagnetics useful? 2

Answer 12

1.switch on and off are really useful.=quick to turn on and off
2.they can create a varying force.

Question 13

How does the electromagnet create an electric bell in circuit? 5

Answer 13

1.button is pressed, a current flows through the coil
2.coil attracts the iron bar, causing the clapper to hit the bell
3.causes the contact to break the circuit
4.electromagnet turns off and the bar moves back to it’s original position, reconnecting the circuit
5.electromagnet turns back on and the cycle repeats

Question 14

motor effect?

Answer 14

A wire carrying a current creates a magnetic field. interact with another magnetic field=force that pushes the wire at right angles

Question 15

What angle does the wire have to be at to experience the motor effect (3)?

Answer 15

.90° to the magnetic field.
.wire runs parallel to magnetic field= no force at all.
.At angles in between, it’ll feel some force.

Question 16

Force acting on a conductor in a magnetic field depends on three things? (motor effect)

Answer 16

1)magnetic flux density -how many field (flux) lines there are in a region=strength magnetic field.
2) The size of the current through the conductor.
3) The length of the conductor that’s in the magnetic field.

Question 17

How to find the force acting on it can be found by what equation?

Answer 17

Force (n)= magnetic flux density(T Tesla)x current (a)length(m)

Question 18

How do you tell which ways force is acting?

Answer 18

.Fleming’s left-hand rule.
1)Using your left hand, point your First finger in the direction of the Field.
2) Point your second finger in the direction of the Current.
3) Your thumb will then point in the direction of the force (Motion).
=shows that if either the current or the magnetic field is reversed, then the direction
of the force will also be reversed. .

Question 19

Why does a Current-Carrying Coil of Wire Rotates in a Magnetic Field in a basic dc motor? 3
How can you reverse the current?

Answer 19

1)Forces act on the two side of a coil of wire that’s carrying a current.
2)Because the coil on a spindle and the forces act one up and one down, it rotates. forces cause the moments to act in the same direction
3) split-ring commutator and swap from one carbon brush to the other, swapping the direction current every half turn to keep motor rotating same direction.
4)reversed=swapping polarity of the dc supply (reversing the current), swapping magnetic poles (reversing the field).

Question 20

How do the loudspeakers work using the motor effect? 6

Answer 20

1-cone with coil wrapped around one end connected to Ac supply
2-permanet magnet which goes inside the coil of wire
3- as a current passes through coil it generates a magnetic field
4-the magnetic field from the permeant magnet interacts with the other magnetic field ether attract or repl
5-produces a resultant force which causes the cone to move
6-when the current switches direction the force reverses
7-move in and out generating soundwaves

higher frequency= higher pitch (change frequency od ac supply)
higher current bigger ampluitde of sound larger volume

Question 21

What is the generator effect?

Answer 21

when an electrical conductor moves in a magnetic field through the field lines

The generator effect is the generation of a current in a wire moving relative to a magnetic field.
there’s a change in the magnetic field around an electrical conductor

potential difference is induced across the conductor.

Question 22

How does Cutting Field Lines Induces a Potential Difference and voltage?
Effects of an induced current?

Answer 22

-move magnet around a coil of wire=potential difference.
-complete circuit= induced current not complete means induced potential difference

Effects of the induced Current:
• Induced currents create magnetic fields.
• magnetic field oppose magnet and swaps poles when inserted to repel and the attract

Question 23

How Can Change the Size of the Induced Potential Difference?

Answer 23

1)Increasing speed movement=cutting more magnetic field lines given time.
2) Increasing strength magnetic field= more field lines that can be cut.

Question 24

How do Alternators Generate Alternating Current?
(generator effect)
What are the slip rings for?

Answer 24

1- coil rotated in a magnetic field
2-potential difference is induced in rotating coil and AC current flows
3- slip rings connected to the coil brushes make continuous contact
4-As the rotation continues and side coil moves down, the induced potential difference reverses direction AC

Question 25

How do Dynamos Generate Direct Current?

Answer 25

1-coil of wire rotates in a magnetic field
2-split ring commutator changes the coil connections every half turn
3-connections of the coil with split ring commutator are reversed
4- this means that the current to the external circuit alwavs flows in the same direction

Question 26

What does the oscilloscope do?
What is AC?
What is DC?
What is the height?
What is the increasing revolutions what happens when you
Increase the frequency?

Answer 26

1)Oscilloscopes=PD generated in the coil changes over time.
2) ac=line that goes up and down, crossing horizontal axis.
3) dc=line above axis (pd positive)
4) height line= given point generated PD at that time.
5) Increasing the frequency of revolutions increases the overall pd=creates more peaks

Question 27

How do Microphones Generate Current From Sound Waves?(generator effect) 4

Answer 27

1) Sound waves hit diaphragm attached to a coil of wire, wrapped around magnet.
2)causing coil of wire to vibrate move in magnetic field
3) the coil / wire cuts magnetic field lines
4) potential difference is induced

Question 28

How do Transformers Change? 5
• insulation prevents current flowing through the iron core

Answer 28

1.primary coil is connected to an alternating current
2.primary coil current produces a alternating magnetic field
3. it is transmitted across the iron core and passes through the secondary coil
4.the changing magnetic field induces a changing potential difference in the secondary coil
5.induced potential difference produces an alternating current in the external circuit

Question 29

STEP-UP TRANSFORMERS?

Answer 29

.step the potential difference up (i.e. increase it). more turns on the secondary coil than the primary coil.

Question 30

STEP-DOWN TRANSFORMERS ?

Answer 30

step the potential difference down (i.e. decrease it). more turns on the primary coil than the secondary.

Question 31

The Transformer Equation calculate the PD output?

Answer 31

1)input pd and number of turns on each coil, calculate output transformer using the transformer equation:
2) less rearranging to do if you put whatever you’re trying to find on the top. As the equation can swap what on top.