6 Magnetism Flashcards
1
Q
Magnet
A
- Object that has a magnetic field around it
- Can exert a non-contact force on another nearby magnet or magnetic material
- Like poles repel, unlike poles attract
- Iron, Cobalt, and Nickel are magnetic
2
Q
Magnetically hard
A
- Produces its own magnetic field
- Permanent
3
Q
Magnetically soft
A
- Magnetism can be induced into it through a magnetic field
- Temporal
4
Q
Uniform magnetic field
A
- Magnetic field lines are parallel, straight and evenly spaced
- Place two bar magnets, opposite poles facing each other at a short distance apart
5
Q
Find magnetic field shape and strength
A
- Place bar magnet under a piece of paper
- Shake iron filling onto the paper, tap the paper
- The shape of the field can be seen around the magnet
- The closer the iron fillings, the stronger the field in that area
6
Q
Find magnetic field direction
A
- Place the bar magnet under a piece of paper
- Surround the bar magnet with plotting compasses, arranged in a semicircle
The needle of each plotting compass lines up with the field line
7
Q
Magnetic field line
A
- The lines used to represent a magnetic field
- From North to South
8
Q
Electromagnet
A
- When current flows in a wire, a magnetic field is produced around the wire
- Increasing the current will increase the strength of the field produced
9
Q
Single straight wire field pattern
A
- Right-hand rule,: thumb-current, finger-field
10
Q
Solenoid
A
- Wire coiled up in a spiral shape
- When current flows, field shape is similar to bar magnet field
- Field inside is strong and uniform
- Small field in each coil adds up to make a stronger overall magnetic field
11
Q
Electromagnet construction
A
- A solenoid with an iron core
- Iron core increases the solenoid’s magnetic field strength
- Made by coiling a wire around an iron core
Make stronger by:
- Increasing current
- Increasing the number of coils
- Using an iron core
12
Q
Motor effect
A
- A force on a charged particle is exerted when it moves in a magnetic field as long as its motion is not parallel to the field
- Use Fleming’s left-hand rule: Thumb-Motion, First finger-field direction (N to S), Second finger-Conventional current (+ to -)
13
Q
D.C motor
A
- When current flows through the coil, a magnetic field is created. If the coil current doesn’t flow parallel to the magnetic field, a force is exerted on the coil since the coil’s field interacts with the magnetic field.
- When parallel to the magnetic field, the split ring commutator swaps the contacts of the coil and reverses the current direction so the motor keeps spinning in the same direction. The commutator has split which briefly disconnects the current to allow momentum to keep coil turning until magnetic field force takes over again
14
Q
Loudspeaker
A
- A.C. current in the coil creates a magnetic field
- A.C. current in the coil of the wire interacts with the permanent magnetic field
- Force is generated following FLHR
- The coil attached to the core of the speaker causes the core to oscillate back and forth with the coil
- Core oscillations move the air at the A.C. frequency
- This generates sound waves
15
Q
Induction
A
- When a magnetic field cuts through a conductor, a voltage is induced, resulting in the flow of electric current
- When the magnet stops moving, no voltage is induced so no current flows
- If a magnet moves in and out, A.C. is induced
16
Q
Induction factors
A
To produce a larger current:
- Stronger magnet
- Faster magnet
- More coils
17
Q
Transformer
A
- A machine that can transform a voltage into a higher (step-up) or lower (step-down) voltage
- Iron core with two opposite coils
18
Q
Transformer functioning
A
- A.C. in primary coil turns the iron core into an electromagnet
- Since the current is A.C., the field moves and changes direction
- The moving field induces a current on the secondary coil
- Vp (V) / Vs (V) = np / ns
- Vp (V) x Ip (A) = Vs (V) x Is (A)
More coils in secondary - step-up
More coils in primary - step-down
19
Q
Transformer in the national grid
A
- Transformers are used to increase efficiency
- They step up the voltage to decrease current to decrease resistance effect to the wire heat up less
- Before it is supplied to individuals, voltage is stepped down and current is increased
20
Q
Change wire direction
A
- Change current direction
21
Q
Generator
A
Electricity can be generated by either moving a magnet inside a coil or rotating a coil inside a magnetic field.
- Coil is rotated within a magnetic field
- As it turns, the coil cuts the magnetic field lines
- This induces a voltage/current in the coil
- This can then be contened to a circuit
In a generator, kinetic energy is converted into electrical energy
