P5 Flashcards
How are objects attracted to eachother after object is rubbed against one’s hair or other suface?
It is attracted as during the process of rubbing in gain or losses electrons, which make it positvely or negatively charged
An example of this is rubbing a baloon against your hair and then seeing how it is able to stick to walls, as it is attracted to them
What is one model for an electric circuit?
+ photo
- hear the mouse represents the battery
- and the are charge - through the movement of the mouse
- the paddle wheel causes resistance, causing energy to be used in the circuit.
What way does conventional current and which way does the electrons flow?
- covential current flows clockwise in a closed circuit from + to -
- electrons flow anticlockwise in a closed circuit from - to +
What is an electric current and how is it measured?
- electric current is the flow of charge around a closed circuit
- greater current, more energy it can transfers
- an anmeter is used to measure the current
- slows the amount of charge going through the meter every second
- how it is connected in a circuit
What fact remains constant about electric current in a series circuit?
the speed remains constant
What are some more facts about current?
- the current is not used up when it flows around the circuit
- the charge is used up and transfered
Name two types of circuits?
- a parallel circuit
- a series circuit
What causes resistance?
- lamps
- resistors
- wire a little bit
How do wire get hot when current flows through them?
- charges in the metal= electrons
- ion collide with the lattice structure of the wire
- cause energy to be transferred
- some metals have wider lattice structures which craetes less resistance for the ions or charges traveling through the wire
How is resistance measured in a series and parallel circuit?
-series circuit
R1+R2= R3
-Parallel circuit
R3=1 divided by 1 over R1+ 1 over R2+1 over Rn
What determines the size of the current?
- the voltage of the battery
- the resistance of the circuit compoents
How is a voltmeter connected in a circuit, and what happens when more voltage goes through a lamp?
- connect across the compoent
- more voltage= brighter the lamp
What is voltage?
- the voltage is the push of the current around the circuit
What is resistance?
- this is a force that means more energy is required to push the current
- the resistance effects the size of the current?
What is the formula for the resistance of a conductor?
resistance of a conductor= photo
What is a fact about current and voltage?
- current in circuit is proportional to the voltage of the battery
- this is known as ohm’s law
resistance= the voltage divide by current
What is a variable resistor?
- its resistance can be changed or varied by moving a slider or dial
- more coils of wire the current has to go through, the greater the resistance
What bis an light dependent resistor?
- the more light it is exposed tp the greater the resistance
What is a thermistor?
- increases resistance according to to temperature
- lower ressitance - hotter
What is potentail difference?
- higher potentail energy at the begining
- lowest potential energy after the last compoent
What does a voltmeter measure ?
- the potentail difference between two points e.g.
A to B
How do you measure the power of a circuit and work done?
What is the link between magnetism and electricity?
- when there is an electric current there is a magnetic field in the region of the wire
- winding the wire round in a coil
it strengthens the magnetic force
- each turn of the wire has its own magnetic field, which is added together
What is an electromagnet?
- a wire coil around an iron core with a current running through it
- can be switched on and off
How does an electric motor work?
- a permenant magnet(compass needle) experiences a force if placed in a magnetic field
+photo
- no forces at the two ends of the coil
- yet is aforce on the two sides of the coil
- forces will be at right angles to both the magnetic field and the current
- one force is up
- other is down
- cause turning effect
- coil is made with several turns of wir
- stronger the turning force
+photo
- in a electric motor
- once the coil has turned 90 degrees, the direction of the current is reversed
- makes the turning continuous
Hoe is the current of an electric motor reversed in direction?
- by using a split ring commutor- pair of rings and brushes
- no fixed wires in motors
- half the ring rubs against the brush for half a turn
- changes direction of the current
How does a generator work?
- this is done by moving a magnet near to a coil of wire
- current only, when the magent is moving
What is an electromagnetic induction?
=photo
- this occurs when the magnet is removed from inside the coil
- there is a smaal current in the opposite direction to the original current
How did Faraday believe a generator to work?
- no movement - no voltage
- magnet- moving - the magnetic field is changing
- magnetic field lines arew cutting the coil
- causes potential difference or voltage across the coil
- in a complete circuit , voltage causes a current
- magnet + coil behaves like a battery
- when athe magnet is removed from the coil
- the field changes
- causes induced voltage in the opposite direction of the current
What is a. c. and d. c.
alternating current produced by generator
- current goes in two directions positive negative on a graph
- changing magnetic field
- direct current
- from a battery and travels in one direction
How can the size of alternating voltage produced by a generator be incraesed?
- stronger rotating magnet or electromegnet
- rotating it faster
- using a fixed coil with more turns
- putting an iron core inside the fixed coil
- strength of the magnetic field is in increased
How can the size of induced voltage be increased?
- moving the magnet in and out more quickly
- stronger magnet
- using a coil with more turns
How does a transformer work?
- changed the current in the primary coil induces the voltage in the secondary coil
- output of the transformer depends on the number of coil of wire
- more in secondary then primary
- step up transformer
- voltage increases
- yet current in the secondary coil will be less
- no greater power supplied
P=IV
What is the formula for the output of a tranformer?
What was fleming left hand rule?
