P5 Flashcards
Describe the forces between magnets
North and South Pole
Like poles -> repulsion
Opposite poles -> attraction
What is a magnetic field?
Region around a magnet where it has magnetic effects on a magnetic material (force experienced)
Describe the forces between a magnet and a magnetic material
A magnetic material experiences a force when in a magnetic field
If the material is un magnetized -> always attracted to magnet
If the material is magnetized -> forms a magnet and acts like one
What is induced magnetism?
When iron (or a metal with magnetic properties) it can be magnetized via different methods to turn it into a magnet
Induced magnet -> temporarily magnetic (ex: soft iron)
Permanent magnet -> doesn’t lose magnetism (ex: hard iron/steel)
How can a magnetic material be magnetized?
- Stroking a magnet along the object from one end to the other repeatedly
- Holding the object in a magnetic field and hitting it
- Putting the object in a strong magnetic field
How can you demagnetize a magnet?
Hitting (outside of a magnetic field) or heating
Draw the field lines around a bar magnet
Make sure:
The arrows go from N -> S (convention)
Lines never cross
Lines are closer together when they are closer to the magnet
What happens to domains in a magnetic material when it becomes magnetized ?
Un magnetized -> domains unaligned
Magnetized -> domain aligned
What are the magnetic properties of soft and hard iron?
Soft iron:
Easily magnetized
Cannot retain magnetism
Good for electromagnets
Steel/hard iron:
Hard to magnetize
Retains magnetism
Used to create permanent magnets
What are the properties of permanent and electromagnets?
Permanent:
Permanently magnetized -> cannot be turned on/off
Electrons have intrinsic magnetic field which add up to create one big magnetic field
Electromagnets:
Becomes magnetized when electricity is flowing through it
Charged particles move through a space and INDUCE a magnetic field
What is charge measured in?
Coulombs (C)
T of F: like charges attract
F: unlike charges attract and like charges repel
Describe an experiment that can be done to show the production and detection of electrostatic charge by friction
Inflate balloon -> rub against fabric -> turn on tap -> hold balloon next to water -> water bends towards balloon
A result of the charges of the materials:
Balloon -> negative
Water -> positive particles are attracted to negative balloon
How is a material charged?
When 2 insulators are rubbed together -> oppositely charged
Electrons removed from one material (now Pos)
Electrons lost go to the other material (now neg)
To discharge -> touch conductor or earth
What is electrostatic induction?
When a charged object is held near an uncharged one -> the opposite charge is induced to the side closest to the charged object
What is the equation for electric field strength?
E = electric field strength
F = force (in newtons)
Q = charge (in coulombs)
E = F/Q
What is an electric field?
A region in which an electric charge experiences a force
What are electrical conductors and insulators ?
Conductors:
Current can flow through
Ex: silver, copper, aluminum, steel
Insulators:
Doesn’t allow flow of charge/current
Ex: plastic, wood, glass, rubber, acetate
What is current?
The flow of electrons/charge in a circuit
Convention current goes from Pos -> neg
Reality -> other way/ movement of electrons
Measured in Amps (A)
What is potential difference/voltage?
Work done by a unit of charge passing through a component
Must exist for current to flow -> think of its as pushing the current
(in a series circuit) power/pd is used to push, so there will be a difference in energy between the beginning and end of the component
Measured in volts (V)
What is emf?
Electromotive force
Sum of all voltage
Work done by a power source in moving a unit of charge -> around the ENTIRE CIRCUIT
Electrical source of energy
Measured in volts (V)
What is resistance?
The opposition to a current (measured by how difficult it is to push the current)
Measured on Ohms ( Ω )
What is an equation for current? (Using charge)
Current -> rate of flow of charge at a given point
I = current
Q = charge
t = time
I = Q/t
Why is metal a good conductor?
Metals -> loose electrons
Current is the flow of these electrons, and since they can move freely and carry charge it makes metal a good conductor
What is the use of an ammeter (analogue and digital)?
Measured current
Connected in series
What is the use of a voltmeter (analogue and digital)?
Mesures voltage
Connected in parallel
What is an equation for current?
R = V (voltage)/ I (current)
A change in voltage or current causes a change in resistance
What is a resistor?
A device with a specific resistance
Current-voltage graph -> straight line through the center (gradient +1)
What does the current voltage graph of a filament lamp look like like?
Curved -> checks notes
When the line flattens the wire has melted
How does heat relate to resistance?
Wire heats -> atoms shake more -> more resistance -> more heat
How does length and diameter of the wire affect resistance?
Longer -> electrons collide more with ions -> more resistance
Diameter bigger -> more space for electrons to flow -> less resistance
What is electric power measured in?
Watts (W)
Joules/s
