Electromagnetism Flashcards
(22 cards)
What is a magnetic field?
A region where magnetic materials experience a force
Which direction do magnetic field lines point?
From north to south
3 magnetic metals?
Iron,nickel and copper
What does magnetically soft mean?
Easy to magnetise and de magnetise (eg iron)
What does magnetically hard mean?
Difficult to magnetise and demagnetise (eg steel)
Explain experiment 1 (iron fillings)
-Place a magnet under paper
-put iron fillings on the top and tap paper
-should show magnetic field lines
What are the advantages and disadvantages of experiment 1?(iron fillings)
-precise and allows clear image
-can’t see direction
Explain experiment 2(plotting compass)
-place magnet on paper
-mark North Pole
-move compass around magnet
-mark North Pole again
Advantages and disadvantages of experiment 2?(plotting compass)
-shows clear direction
-low resolution field lines
What is the right hand grip rule used to find?
Direction of Current and magnetic field
In the right hand grip rule what do the thumb and fingers represent?
Thumb- current
Fingers- magnetic field
What is a solenoid?
A solenoid is a cylinder coil of wire acting as a magnet when carrying electric current.
Explain the motor effect
When a current-carrying wire is put between magnetic poles, the two magnetic fields affect on another. This result is a force on the wire. This can cause the wire to move.
What does flemmings left hand rule tell you?
Movement
Magnetic field (N to S
Current (+ to -)
In Flemings left hand rule, what does the thumb represent
Movement
In Flemings left hand rule, what does the first finger represent
Field (magnetic field)
North to south
In Flemings left hand rule, what does the second finger represent
Current
(+ to -)
In a simple direct current electric motor what 4 factors can speed it up
-higher current
-more coils
-a soft iron core
-stronger magnetic coil
How do loudspeakers work?
-a.c electrical signals from an amplifier are fed to a coil of wire in the speaker which is wrapped around the base of a cone
-the coil is surrounded by a permanent magnet so the a.c signals cause a force on the coil and make it move back and forth
-these movements cause the cone to vibrate and creates sounds
What is electromagnetic induction?
The creation of a voltage (and maybe current) in a wire which is experiencing a change in magnetic field
What are 2 ways of generating electricity
-move a coil of wire in a permanent magnetic field
-move/rotate a permanent magnet within a coil of wire
How to increase voltage/current?
-increase number of coils
-use a stronger magnet
-move magnet faster
