P3 Flashcards
What is static electricity?
When you transfer electrons between surfaces when rubbing them together
What is an electric field?
It is the space surrounding any electric charge, where its affects can be felt
What is current?
- It is the rate of flow of electrical charge
- It only flows if a circuit is closed
- transfers energy from a power supply
What is potential difference?
- It is the driving force that pushes the charge around
- Measured in volts
- The work done per unit of charge
What are the different potential difference equations?
1)potential difference(V)=current(A) x resistance(ohms)
2)Potential difference(V)=work done(J) x chargew(C)
What is power?
- The rate of energy transfer
- Measured in watts(W) which is J/s
What are the different power equations?
- power(W)=energy(J)/time(s)
- power(W)=potential difference(V) x current(A)
What are series circuits?
- The components are connected in a line, end to end
- potential difference is shared between the components
- Current is the same at all points of the circuit
- The resistance of the resistors add up
What are parralel circuits?
- The components are spread apart in different branches that are parallel
- Potential difference is the same across branches- if one branch has two resistors that total to a p.d of 5V and another branch has 1 then that branch will also have 5V of p.d
- The current is shared between the branches
- Resistance will always be lower than the lowest amount of resistance
What are magnets?
- Something that has 2 poles- a north and a south pole
- Magnetic field is produced where other magnetic materials or magnets experience a non-contact force to attract to each other
- The lines of the magnetic field when being draens always go from north to south
- The closer the lines are the stronger the magnetic field is, the further away they are the weaker the field is
What are the two types of magnets?
Permanent-produce their own magnetic field
induced-turn into magnets when put in a magnetic field
What is the right hand thumb rule?
- used to show the direction of current and the direction of the magnetic field
- the thumb is current
- your index finger is the magnetic field
What is the motor effect?
- When a current carrying conductor is put neat a permanent magnetic, the two magnetic fields interact with each other
- this causes a force to be exerted on the wire and the magnet
- This is the motor effect
What is flemings left hand rule?
- Used to find the direction of the force on a current carrying conductor that is at right angles to a magnetic field
- Thumb-Force
- index finger-magnetic field
- middle finger-current
- A GOOD WAY TO REMEMBER IT IS Father Mother Child
How do you calculate the force acting on a current carrying conductor?
Force(N)=magnetic flux density(T)xCurrent(A)xLength of conductor(m)
What are simple electric motors?
W
- current flows in different directions on each side of the coil, each side is perpendicular to the the magnetic field, each side exeperiences forces in opposite directions
- Because the coil is on a spindle, and the forces act in opposite directions on each side, it rotates
- The split ring commutator is a clever way of swapping the contacts every half turn to keep the motot rotating in the same direction
- the direction fo the motor can be reversed by reversing the current or swapping the magnetic poles
How do loudspeakers use magnets and a coil of wire?
- The force between a current-carrying coil of a wire and a magnetic field can be used to make things move back and forth
- Contains a coil of wire which surrounds one pole of a permanent magnet, the other pole surrounds the coil
- Alternating current flows through the coilvof wire, which is wrapped around the base of a cone.
- The interaction between the madnetics fields of the magnet and the coil forces the coil to move in one directions, forcing the coil back in the other direction
- As current alternates, the coil moves back and forth
- The size of the force depends on the size of the current in the coil
- Makes the cone vibrate-therefore the vibrations in the air are caused, the sound
What is work done?
- Transferring energy in the form of motion from one store to another
- Measured in joules(J)
- Potential difference(V) = Work done(J) x Charge(C)
What are alternators and dynamos?
- They are two types of generators
- Dynamos have a split ring commutator
- Altenators have slip rings and brushes
How do loudspeakers work?
1)Current floes through the coil
2)This causes the diapraghm
3)Magnetic field from coil interacts with magnetic field of permanent magnet
4)The cone then experiences a force
5)When current is reversed the magnetic field reverses
6)Therefore the force is in opposing direction causing sound to be produced
How do microphones work?
1)Sound waves will hit a diapraghm
2)This causes the diapraghm and coil of wire to move
3)As wire is moving within the magnetic field of permanent magnet, it will generate a current(electromagnetic induction/ generator effect
4)The frequeny and amplitude of the sound waves determine the frequency and amplitute of the wave
